The Art of Photography A guide to digital Photography

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SHUTTER | TUTORIALS www.shuttertutorials.wordpress.com | www.facebook.com/ShutterTutorials

Author Tanay Shandilya CONTENT

WORKING OF A DSLR CAMERA

THE SENSOR AND CUP

UNDERSTANDING LIGHT

DYNAMIC RANGE

UNDERSTANDING ISO

EXPOSURE

CAMERA SHUTTER SPEED

UNDERSTANDING CAMERA LENSES

UNDERSTANDING PHOTOGRAPHY ‘CIRCLE OF CONFUSION’

OPTICAL ZOOMING PERSPECTIVE CHANGE

THE HISTOGRAM

FULL FRAME v/s CROPPED SENSOR

GET TO KNOW FLASH PHOTOGRAPHY Working Of A DSLR Camera

A camera based on the single-lens reflex (SLR) principle uses a mirror to show in a viewfinder the image that will be captured.

The cross-section (side-view) of the optical components of an SLR shows how the light passes through the lens assembly

(1), is reflected into the pentaprism by the reflex mirror (which must be at an exact 45 degree angle)

(2) and is projected on the matte focusing screen

(3) opens, and the image is projected and captured on the sensor

(4), after which actions, the shutter closes, the mirror returns to the 45 degree angle, the diaphragm reopens, and the built in drive mechanism re-tensions the shutter for the next exposure.

(5). Via a condensing lens

(6) and internal reflections in the roof penta-prism.

(7) the image is projected through the eyepiece

(8) to the photographer‘s eye. Focusing is either automatic, activated by pressing half-way on the shutter release or a dedicated AF button, as is mainly the case with an autofocusing film SLR; or manual, where the photographer manually focuses the lens by turning a lens ring on the lens barrel. When an image is photographed, the mirror swings upwards in the direction of the arrow, the focal-plane shutter. There is often a ring of soft material around the focusing screen, which helps to both cushion the impact of the mirror slapping up and helps seal the mirror box from light entering through the eye piece. Some high end cameras incorporate a shutter into the eyepiece to further eliminate light that may enter there during long exposures. Phase-detection autofocus. The diagram shown here is an over-simplification in that it omits the sensors used to activate the drive for the autofocus system. Those sensors reside at the bottom of the mirror box. In such a system, the main mirror is slightly translucent in the center, which allows light to pass through it to a secondary mirror which reflects light to the sensors below. DSLRs typically use a phase detection autofocus system. This method of focus is very fast, and results in less focus ―searching‖, but requires the incorporation of a special sensor into the optical path, so it is usually only used in SLR designs. Digicams that use the main sensor to create a live preview on the LCD or electronic viewfinder must use contrast-detect autofocus instead, which is slower in some implementations. DSLR optical viewfinder vs. digital point-and-shoot camera LCD Depending on the viewing position of the reflex mirror (down or up), the light from the scene can only reach either the viewfinder or the sensor. Therefore, many older DSLRs do not provide ―live preview‖ (allowing focusing, framing, and depth-of-field preview using the display), a facility that is always available on digicams although today most DSLRs offer live view. The advantages of an optical viewfinder are that it alleviates eye-strain sometimes caused by electronic view finders (EVF), and that it constantly shows (except during the time for the sensor to be exposed) the exact image that will be exposed because its light is routed directly from the lens itself.

Compared to ordinary digital cameras with their LCDs and/or electronic viewfinders the advantage is that there is no time lag in the image; it is always correct as it is being ―updated‖ at the speed of light. This is important for action and/or sports photography, or any other situation where the subject or the camera is moving too quickly. Furthermore, the ―resolution‖ of the viewed image is much better than that provided by an LCD or an electronic viewfinder, which can be important if manual focusing is desired for precise focusing, as would be the case in macro photography and ―micro-photography‖ (with a microscope). Compared to some low cost cameras that provide an optical viewfinder that uses a small auxiliary lens, the DSLR design has the advantage of being parallax-free; that is, it never provides an off-axis view.

A disadvantage of the DSLR optical viewfinder system is that while it is used it prevents the possibility of using the LCD for viewing and composing the picture before taking it. Some people prefer to compose pictures on the display – for them this has become the de- facto way to use a camera. Electronic viewfinders may also provide a brighter display in low light situations, as the picture can be electronically amplified; conversely, LCDs can be difficult to see in very bright sunlight.

The Sensor and CPU

The sensor is the part of your camera that captures the light exposure filtered through the lens. For our intents and purposes, we‘re just going to call this the image. The way the sensor was produced, and how large or small it is, has a pretty big effect on the end result: your photograph.

First of all, the size of the sensors matters. Compact point-and-shoot cameras have very small sensors and the difference in size between them is a smaller factor when choosing a camera. When it comes to cameras with interchangeable lenses, which include DSLRs and MILC/CSC/EVIL cameras (which are basically compact, mirrorless DSLR- like cameras that often—but not always—have smaller sensors), sensor size has a greater impact. Generally larger sensors provide better low- light performance, greater control over depth of field, and produce higher resolution images with less noise than a smaller sensor.

The majority of DSLRs have a sensor size most commonly known as APS-C. An APS-C sensor is about half the size of a frame of 35mm film and generally magnifies all lenses by a factor of 1.6x. This means that using a 35mm lens on a DSLR with an APS-C sensor is basically the same as using a 56mm lens on a regular 35mm camera. This is good news for telephoto lenses but bad news for wide angle, as every lens isn‘t as wide as advertised when placed on an APS-C-based camera. A 10mm fish eye lens will produce photos like a 16mm wide-angle lens. It‘s not a major downside for most people, but it‘s important to know.

Some higher-end DSLRs contain full-frame sensors, such as the popular Canon 5D Mark II, which is equivalent to the size of a frame of 35mm film. Full-frame sensor DSLRs have the previously mentioned benefits that come with large sensors, but also are not subject to the 1.6x magnification like you‘ll find with APS-C sensors. Basically, a full- frame sensor DSLR is about as close as you‘re going to get to 35mm film with a digital camera.

While sensor design is very relevant to the image quality, and the only way you‘re going to be able to judge that quality for certain is to see or produce sample images, you should pay attention to the sensor‘s megapixel rating. In general, the more megapixels packed into a sensor the more noise you‘ll find in a given image. This is why you don‘t necessarily want to choose a camera with a high megapixel rating—especially when a camera has a smaller sensor. For most people, even a 6.3 megapixel camera is sufficient, but anywhere from 8-10 should be more than sufficient. The point is, don‘t just buy one camera over the other because it has a higher megapixel count. It may produce noisier, less-desirable results so you should always test first.

Understanding Light

The Three Properties of Light Today is one of those days that I wanted to take a step back to some basics again. This time I want to talk about the three primary properties of light, and since what we are doing as photographers is recording light, it is important to know how these properties play into getting a good image. While I had studied this before, attending a recent seminar from Ed Pierce made me realize that many reader may never have seen these concepts before. Quantity The first property of light that we want to look at is Quantity. This is the amount of light that is hitting the subject. You have several ways of adjusting the amount of light the camera will see. In some cases you can adjust the light output of your lights or use diffusers to cut down on the light if you have too much. You should all know that you can also adjust your aperture or shutter to adjust the amount of light coming into the camera. With DSLR‘s, don‘t forget you can also adjust your ISO setting. With four main ways to adjust for light quantity, this is one of the more versatile of the three properties. Quality The light quality is one of the more confusing properties and the one that gives new photographers the most trouble. Quality is not about the color of the light, it refers to whether the light is very harsh and will cause hard shadows, or is it softer with smoother shadows. The quality of the light will affect the overall contrast. The way we adjust the quality of light is by changing the apparent size of the light source. The reason this is confusing is that you initially think that the close a light is to the subject, the harsher the light will be. In fact, the exact opposite is true. The closer the light is to the subject, the larger the light source will appear to be. Take the Sun as an example, far and away the largest object in our solar system, but because of the distance, it acts as a very small diameter light source causing harsh shadows. If you only have a small lightbox, moving it close to the subject will make it appear much larger and thus will soften the shadows and provide a more pleasing light source. Direction The third property should be fairly simple to understand. The light direction will also affect shadows and the final image quality If you are using small lights, you can simply move them in order to create a more flattering light angle. If you are using window light, or other unmovable light source than you can still change the orientation of the subject to the light source.

Dynamic Range

Dynamic Range of a Sensor

The dynamic range of a sensor is defined by the largest possible signal divided by the smallest possible signal it can generate. The largest possible signal is directly proportional to the full well capacity of the pixel. The lowest signal is the noise level when the sensor is not exposed to any light, also called the ―noise floor‖. Practically, cameras with a large dynamic range are able to capture shadow detail and highlight detail at the same time. Dynamic range should not be confused with tonal range. Dynamic Range of an Image

When shooting in JPEG, the rather contrasty tonal curves applied by the camera may clip shadow and highlight detail which was present in the RAW data. RAW images preserve the dynamic range of the sensor and allow you to compress the dynamic range and tonal range by applying a proper tonal curve so that the whole dynamic range is represented on a monitor or print in a way that is pleasing to the eye. This is similar to the more extreme example in the tonal range topic which shows how the larger dynamic range and tonal range of a 32 bit floating point image were compressed. Pixel Size and Dynamic Range

We learned earlier that a digital camera sensor has millions of pixels collecting photons during the exposure of the sensor. You could compare this process to millions of tiny buckets collecting rain water. The brighter the captured area, the more photons are collected. After the exposure, the level of each bucket is assigned a discrete value as is explained in the analog to digital conversion topic. Empty and full buckets are assigned values of ―0‖ and ―255‖ respectively, and represent pure black and pure white, as perceived by the sensor. The conceptual sensor below has only 16 pixels. Those pixels which capture the bright parts of the scene get filled up very quickly. Once they are full, they overflow (this can also cause blooming). What flows over gets lost, as indicated in red, and the values of these buckets all become 255, while they actually should have been different. In other words, detail is lost. This causes ―clipped highlights‖ as explained in the histogram section. On the other hand, if you reduce the exposure time to prevent further highlight clipping, as we did in the above example, then many of the pixels which correspond to the darker areas of the scene may not have had enough time to capture any photons and might still have value zero (hence the term ―clipped shadows‖ as all the values are zero, while in reality there might be minor differences).

One of the reasons that digital SLRs have a larger dynamic range is that their sensors have larger pixels. All things equal (in particular fill factor, ―bucket‖ depth, and exposure time), pixels with a larger exposed surface can collect more photons in the shadow areas than small pixels during the exposure time that is needed to prevent the bright pixels from overflowing.

It is easy to understand that one of the reasons digital SLRs have a larger dynamic range is that their pixels are larger. Larger pixels can collect more photons in the shadow areas before the bright ones start to overflow.

Understanding ISO It is challenging to take good pictures without a good understanding of how ISO works and what it does. Camera ISO is one of the three pillars of photography (the other two being Aperture and Shutter Speed) and every photographer should thoroughly understand it, to get the most out of their equipment. Since this article is for beginners in photography, I will try to explain ISO as simple as I can.

Before we go any further, you should first understand how DSLR cameras work.

1) What is ISO ? In very basic terms, ISO is the level of sensitivity of your camera to available light. The lower the ISO number, the less sensitive it is to the light, while a higher ISO number increases the sensitivity of your camera. The component within your camera that can change sensitivity is called ―image sensor‖ or simply ―sensor‖. It is the most important (and most expensive) part of a camera and it is responsible for gathering light and transforming it into an image. With increased sensitivity, your camera sensor can capture images in low-light environments without having to use a flash. But higher sensitivity comes at an expense – it adds grain or ―noise‖ to the pictures.

ISO 200 and ISO 3200 Comparison The difference is clear – the image on the right hand side at ISO 3200 has a lot more noise in it, than the one on the left at ISO 200.

Every camera has something called ―Base ISO―, which is typically the lowest ISO number of the sensor that can produce the highest image quality, without adding noise to the picture. On most of the new Nikon cameras such as Nikon D5100, the base ISO is typically 200, while most Canon digital cameras have the base ISO of 100. So, optimally, you should always try to stick to the base ISO to get the highest image quality. However, it is not always possible to do so, especially when working in low-light conditions.

Typically, ISO numbers start from 100-200 (Base ISO) and increment in value in geometric progression (power of two). So, the ISO sequence is: 100, 200, 400, 800, 1600, 3200, 6400 and etc. The important thing to understand, is that each step between the numbers effectively doubles the sensitivity of the sensor. So, ISO 200 is twice more sensitive than ISO 100, while ISO 400 is twice more sensitive than ISO 200. This makes ISO 400 four times more sensitive to light than ISO 100, and ISO 1600 sixteen times more sensitive to light than ISO 100, so on and so forth. What does it mean when a sensor is sixteen times more sensitive to light? It means that it needs sixteen times less time to capture an image!

ISO Speed Example: ISO 100 – 1 second ISO 200 – 1/2 of a second ISO 400 – 1/4 of a second ISO 800 – 1/8 of a second ISO 1600 – 1/16 of a second ISO 3200 – 1/32 of a second In the above ISO Speed Example, if your camera sensor needed exactly 1 second to capture a scene at ISO 100, simply by switching to ISO 800, you can capture the same scene at 1/8th of a second or at 125 milliseconds! That can mean a world of difference in photography, since it can help to freeze motion.

2) When to use low ISO ? As I‘ve said above, you should always try to stick to the lowest ISO (base ISO) of your camera, which is typically ISO 100 or 200, whenever possible. When there is plenty of light, you should always use the lowest ISO, to retain the most detail and to have the highest image quality. There are some cases where you might want to use low ISO in dim or dark environments – for example, if you have your camera mounted on a tripod or sitting on a flat surface. In that case, bear in mind that your camera will most likely need more time to capture the scene and anything that is moving is probably going to look like a ghost.

3) When to increase ISO ? You should increase the ISO when there is not enough light for the camera to be able to quickly capture an image. Anytime I shoot indoors without a flash, I set my ISO to a higher number to be able to freeze motion. Other cases where you might want to increase ISO are when you need to get ultra-fast shots, like the bird picture I posted above. But before increasing the ISO, you should think if it is OK for you to introduce noise to the image.

On many of the newer DSLRs, there is a setting for ―Auto ISO‖, which works great in low-light environments. The beauty of this setting, is that you can set the maximum ISO to a certain number, so when the ISO is automatically increased based on the amount of light, it does not cross the set barrier. So, if I want to limit the amount of grain in my pictures, I typically set the maximum ISO to 800.

If you have any questions, comments or feedback, please post them in the comments section below. Please note that the above explanation of ISO is given in very basic/simple terms, similar to film sensitivity. Correctly defining ISO in digital cameras can get fairly complex.

Exposure

Understanding Exposure – ISO, Aperture and Shutter Speed ExplainedWhen you think of the craft or art of photography, you must immediately think of exposure. Exposure is a critical element that determines what is actually recorded on film or the image sensor. There are three adjustable elements that control the exposure – ISO, Aperture and Shutter Speed. 1 What controls exposure?

ISO ratings determine the image sensor‘s sensitivity to light, each value of the rating represents a ―stop‖ of light, and each incremental ISO number (up or down) represents a doubling or halving of the sensor‘s sensitivity to light.The Aperture controls the lens‘ diaphragm, which controls the amount of light traveling through the lens to the film plane. The aperture setting is indicated by the f-number, whereas each f- number represents a ―stop‖ of light. The Shutter Speed indicates the speed in which the curtain opens then closes, and each shutter speed value also represents a ―stop‖ of light. The shutter speed is measured in fractions of a second. The Exposure Triangle – When these three elements are combined, they represent a given exposure value (EV) for a given setting. Any change in any one of the three elements will have a measurable and specific impact on how the remaining two elements react to expose the film frame or image sensor and how the image ultimately looks. For example, if you increase the f-stop, you decrease the size of the lens‘ diaphragm thus reducing the amount of light hitting the image sensor, but also increasing the DOF (depth of field) in the final image. Reducing the shutter speed affects how motion is captured, in that this can cause the background or subject to become blurry. However, reducing shutter speed (keeping the shutter open longer) also increases the amount of light hitting the image sensor, so everything is brighter. Increasing the ISO, allows for shooting in lower light situations, but you increase the amount of digital noise inherent in the photo. It is impossible to make an independent change in one of the elements and not obtain an opposite effect in how the other elements affect the image, and ultimately change the EV.

ISO Speed – ISO Sensitivity ISO is actually an acronym, which stands for International Standards Organization. The ISO rating, which ranges in value from 25 to 3200 (or beyond), indicates the specific light sensitivity. The lower the ISO rating, the less sensitive the image sensor is and therefore the smoother the image, because there is less digital noise in the image. The higher the ISO rating (more sensitive) the stronger the image sensor has to work to establish an effective image, which thereby produces more digital noise (those multi-colored speckles in the shadows and in the midtones). So what is digital noise? It is any light signal that does not originate from the subject, and therefore creates random color in an image. The digital camera engineers have designed the image sensor to perform best at the lowest ISO (just like with film). On most digital cameras this is ISO 100, although some high end DSLRs have a mode that brings the ISO down to 50 or even 25.

Aperture Large vs. Small –

A lens‘s aperture is the opening in the diaphragm that determines the amount of focused light passing through the lens. At a small f-stop, say f/2, a tremendous amount of light passes through, even at a fraction of a second; but at f/22, when the diaphragm is perhaps at its smallest, only a tiny amount of light is let in (even at longer shutter speeds). An interesting thing about the aperture and the f-numbers is that it doesn‘t matter the focal length of the lens as long as the f- number is held constant. This is because the arithmetical equation that determines the f-number indicates that the same amount of light passes through the lens on a 35mm lens as on a 100mm lens, with a shutter speed of 1/125s. The size of the diaphragm is unquestionably different, but the amount of light passing through is the same.

Shutter Speed Comparison – Shutter speed is measured in fractions of a second, and indicates how fast the curtains at the film plane open and close. The shutter speed controls how long light enters the lens and hits the image sensor or film plane. The shutter speed enables you to capture the world in split seconds, but it can also absorb the world at speeds upwards of three and four seconds (or remain continually open up until the photographer wants to close the curtain). Snapping the shutter in a fraction of a second, also gives you control on how motion is recorded. If the shutter speed is faster than the object or background, then the image will be tack sharp. If the shutter speed is slower, then you‘ll get blurred objects. Think about the rain in a rainstorm, how fast is that water falling? Well, at 1/30th the raindrops are streaks of undistinguishable white. But at 1/250th, the raindrops hover in mid air and you can see the full swell of each water drop.

2 What is ‚Auto Bracketing‛?

Auto Bracketing is an exposure technique whereby you can ensure that you have the optimal exposure by taking at least three (3) exposures of the exact same composition with one at the metered EV, one at 1/3 of a stop below the metered EV and one at 1/3 of a stop above the metered EV. So ―Auto Bracketing‖ is a function in which you set the EV value then release the shutter and the camera automatically makes the necessary up and down adjustments to the EV to give you the bracketed exposures. Then you can review the three (or more) exposures, see the subtle but critical differences in the images, and decide which one is the best image for your purposes. In the three images on the right, you might prefer the overexposed (by 2 stops) image because the setting sun is most brilliant. Bracketing was a technique that was popularized from shooting slide film, due to the limited ability to correct the image in the darkroom. Many photographers still use the technique today, so they have the exposure that they want. Having the three bracketed images lowers the amount of post-processing time that they might have to spend.

3 Overexposure & Underexposure

Exposure Comparison, Overexposure to UnderexposureHow do you define overexposure and underexposure, since we said that ―correct‖ exposure is subjective? Simply put, overexposure is when the information in the highlights is effectively unreadable. When there is this type of excessive loss of image information there is no way to ―retrieve‖ that missing information in the digital dark room. Underexposure is pretty much the same concept; except in this case there is no image information contained within the shadows. This non- existant information cannot be retrieved through post processing either. In digital photography, once that image information is gone, there‘s no way to retrieve it. This is not always the case in the photochemical world of film photography. With film (as opposed to digital) processing, it is possible to ―find‖ image information in an excessively underexposed frame, and perhaps ―find‖ image information during the printing process for seriously overexposed images as well.

4 AE LOCK (AEL) - Auto Exposure Lock is a camera setting in which the EV is locked in (when you‘re shooting one of the semi- automatic or fully automatic modes, i.e. Shutter-priority), so that now matter what changes there are to the lighting in the scene, the camera locks in the ISO, Shutter and/or Aperture settings, so you can continually achieve the same EV without having to re-meter the scene.

Conclusion One highly practical advantage to digital photography is that it costs next to nothing to experiment with the camera‘s controls, so go out there and shoot away. You want to become increasingly proficient with all three elements of the exposure triangle, so that you can make adjustments on the fly and know exactly what the resulting effect is going to be.

CAMERA SHUTTER SPEED

A camera‘s shutter speed can control exposure, but it‘s also one of the most powerful creative tools in photography. It can convey motion, freeze action, isolate subjects and smooth water, amongst other abilities. This tutorial describes how to achieve these various effects, in addition to hopefully stimulating other creative ideas for using shutter speed in everyday shots. For a background on how it factors into exposure, also see camera exposure: aperture, ISO and shutter speed.

BACKGROUND A camera‘s shutter is like a curtain* that opens and lets in light to start the exposure, then closes to end it. A photo therefore doesn‘t just capture a moment in time, but instead represents an average of light over a time frame. The term ―shutter speed‖ is used to describe this duration. Whenever a scene contains moving subjects, the choice of shutter speed therefore determines which of these will appear frozen and which will be recorded with a blur. However, one cannot change the shutter speed in isolation — at least not without also affecting the exposure or image quality:

The combinations of ISO speed and f-number (aperture) shown in the image enable an amazingly broad range of selectable shutter speeds. Regardless of the combination, more light enables faster maximum shutter speeds, whereas less light permits slower minimum shutter speeds.

For a given exposure, SLR cameras also typically have a much greater range of selectable shutter speeds than compact cameras. For example, this range is roughly 13-14 stops (or 10,000X) with most SLR cameras, but often just 8-9 stops (or 500X) with compact cameras. See the tutorial on compact vs digital SLR cameras for more on this topic.

*Technical Note: At very short exposure times (typically 1/500 a second or faster) the shutter mechanism works more like a moving slit than a curtain. In that case, the shutter speed instead represents the amount of time that each region of the sensor is exposed to light, not the duration over which light reaches the entire sensor.

CONVEYING MOTION While some might see still photography as restricting, many instead see this as liberating, because still capture enables nearly full control over how motion is conveyed. For instance, should the subject be rendered as an unrecognizable streak, or as a more defined blur? Or should the subject remain sharp, with everything else blurred? These and other choices are all under your control.

Speed . Subjects which are moving faster will appear more blurred. This one is perhaps the most obvious of the three, but just as important. Direction of Motion. Subjects which are moving towards or away from the camera usually won‘t become as blurred as those moving side to side — even if both subjects are moving at the same speed. Magnification . A given subject will appear more blurred if they occupy a greater fraction of your image frame. This is perhaps the least obvious, but is also the one which is most under your control, since subject magnification is the combined effect of focal length and subject distance. Longer focal lengths (more zoom) result in more magnification for a given subject distance, but this also increases the likelihood of blur due to camera shake. *Although not a subject trait, the display size may also be important. Blur which appears optimal in a small size on-screen may appear too pronounced in a large print.

A specific but common application of using shutter speed to convey motion is with moving water. Shutter speeds of around 1/2 a second or longer can make waterfalls appear silky, or waves look like a surreal, low-lying mist.

Move your mouse over the various shutter speeds to the right to see this effect. Note how freezing the motion of splashing water required a shutter speed of 1/400 of a second. Since this is a wide angle photo, a shorter shutter speed could have achieved a similar look if one were instead zoomed into just a portion of the waterfall.

One can also use a slow shutter speed to emphasize a stationary subject amongst movement, such as a person standing still amongst a bustling crowd. Similarly, unique portraits can be achieved using moving trains as a background when the shutter speed is as slow as about 1/10 to 1/2 a second

MOVING WITH THE SUBJECT AND PANNING Instead of blurring the subject, one could instead render everything else blurred. This requires the camera to either be located on the moving subject itself, or aimed in such a way that the image frame moves with the subject (called ―panning‖). panning using a slow shutter speed to make a subject appear to be moving fast panning photo at 1/45 sec and 110mm Alternatively, the panning technique doesn‘t necessarily mean that the camera itself has to travel at the same speed as the subject — just that the image frame has to move this fast. Fortunately, even fast subjects can be captured by slowly pivoting the camera, especially if this subject is far away and you‘re using a telephoto lens. Make sure to aim so that your image frame smoothly follows your subject, while also pressing the shutter button — all in one continuous motion. Setting image stabilization to mode 2 for panning A successful panning shot requires a shutter speed which is just slow enough to cause the background to streak, but just fast enough that the subject still appears sharp. This can be tricky to achieve, so the key with panning is to experiment and take many more shots than you would otherwise. Regardless, longer streaks produce a much more dramatic effect; using an image-stabilized lens that has one-axis* stabilization, or a tripod with a pan-tilt head can help you achieve this.

In addition, panning requires a textured background that isn‘t completely out of focus. Subject backgrounds which are closer will also appear to streak more for a given shutter speed and panning rate.

*Lens Panning Mode. This is called ―mode 2‖ IS on canon lenses; nikon lenses with vibration reduction (VR) automatically switch to panning mode when the lens motion is in one direction.

An added benefit is that panning permits slower shutter speeds than would otherwise be needed to capture a sharp subject. For example, available light might only permit a shutter speed of 1/50 second — which might be insufficient to render a particular moving subject as sharp with a standard shot — but with panning, this shutter speed might be fast enough to make the subject appear sharp.

FREEZING FAST ACTION AND HIGH SPEED MOTION High speed photography is capable of new and exciting representations of subjects in motion, in part because we are incapable of seeing and processing movements which are much faster than a running person. Examples include water droplets, birds in flight and moments in sports, amongst many others.

However, capturing fast-moving subjects can also be challenging. The key is to learn to anticipate when your subject will be in the desired position, since shutter speeds shorter than 1/5th of a second are faster than our own reaction time. Simply reacting and pressing the shutter button will likely miss the moment.

To make matters worse, many cameras also impart a delay between when the shutter button is pressed and the exposure begins (called ―shutter lag‖). With SLR cameras this is often just 1/10 to 1/20 of a second, but with compact cameras this can be as high as 1/2 a second. However, these times exclude the additional 1/2 to 1 second (or more) that it can take your camera to autofocus. Pre-focusing on or near your expected subject location can therefore greatly reduce shutter lag.

Sharp high speed photos also require one to be attentive to variations in subject motion, and to potentially time the shot to coincide with a relative pause in the action. For example, with jumping or racing subjects, try to time your shot for when they‘re at their highest point or are changing directions (and are thus moving the slowest). Even with proper timing, one might also need to set their camera to continuous shot mode (or similarly named setting). The camera can then take a burst of shots while you hold down the shutter button — and hopefully capture just the right moment with one of these. In any case, knowing the necessary shutter speed also takes practice. The following calculator estimates the minimum shutter speed needed to make a moving subject appear sharp.

Shutter Speed Calculator show advanced Camera Settings Lens Focal Length mm Subject Distance Subject Speed in side to side direction Minimum Shutter Speed: Notes: CF = ―crop factor‖ (commonly referred to as the focal length multiplier) Calculator assumes the same sharpness criteria as used to determine depth of field; to instead calculate based on sharpness when viewed at 100% on-screen, use ―show advanced‖ above. The above results are only intended as a rough guide. In general, 1/250 to 1/500 of a second is sufficient to freeze everyday motion of people, but one may require 1/1000 to 1/4000 of a second if subjects are up-close or extraordinarily fast.

Notes on Subject Speed . Just because a subject is moving at a given speed doesn‘t preclude portions of this subject from moving even faster. For example, the arms and legs of a runner might be moving much faster than their body. Furthermore, the above subject speed refers to the speed in the direction across your frame (side to side); you can typically get away with a 4X longer shutter speed for subjects moving directly towards or away from you, and a 2X longer shutter speed for subjects which are moving towards/away from you at an angle. Keep in mind that most cameras are only capable of shutter speeds up to 1/2000 to 1/8000 of a second. If the above calculator indicates that you‘ll need a shutter exceeding the capabilities of your camera, your only other options are to try panning with the subject to offset some of their motion, or to resort to using flash photography. ZOOMING BLUR Another interesting technique is to change the zoom during the exposure itself (often called a ―zoom burst‖). You can achieve this look by (i) setting your camera on a tripod, (ii) using a shutter speed of 1/15 to 1/2 a second, and (iii) twisting the lens‘s zoom ring while also trying to avoid moving the camera itself. One can also try only zooming during part of the exposure to lessen the effect.

This causes subjects to have increasing radial blur near the edges of the frame, with the center appearing more or less unblurred. The effect can be used to draw attention to a central subject, or to make the viewer feel as though they‘re moving rapidly.

The zoom burst technique is usually only possible with SLR cameras, but may also be possible with compact cameras that have manual zoom capabilities. Alternatively, zooming blur can often be perfectly replicated using normal photos and post-processing, such as with Photoshop‘s radial blur filter. ABSTRACT AND ARTISTIC EFFECTS Sometimes photographers will intentionally add camera-shake-induced blur to give their image a unique and artistic effect:example of an artistic effect by blurring lights with a slow shutter speed. One typically needs to use shutter speeds of 1/30 – 1/2 a second (or more) since this is just beyond the limit of hand-holdebility, but not too long that the subject will become smoothed out entirely. Predicting the end result can also be difficult, so these types of shots will likely require many attempts (at potentially different shutter speeds) before you are able to achieve the desired look. Also keep in mind that the painted look is often easier to achieve with filters in Photoshop or other editing software.

CONCLUSIONS AND FURTHER READING We‘ve seen several creative ways of using shutter speed, but what if the amount of light required for a correct exposure prevents you from selecting the desired shutter speed — even after all combinations of ISO speed and aperture have been attempted?

For faster shutter speeds, one can try switching to a lens with a larger maximum aperture, or one can add more light to the scene itself by either changing the shooting location or using a flash. Alternatively, for even slower shutter speeds, one can block some of the light by using a neutral density filter or a polarizing filter, or can use the image averaging technique to create a longer effective exposure. In either case, also make sure that you‘re not accidentally over or under- exposing the photo — and thus potentially shifting your range of available shutter speeds.

Other important points and clarifications are listed below.

Shutter Priority Mode . This camera setting can be a useful tool when the appearance of motion is more important than depth of field, or just for letting you know whether your desired shutter speed is even possible using available light. It allows you to pick a desired shutter speed, then the camera‘s metering tries to combine this with an aperture setting (and potentially ISO speed) that will achieve a correct exposure.

Camera Shake . The above analysis assumes that subject motion is the primary source of blur, but in many photos camera shake can instead be more influential — particularly when using telephoto lenses or with unsteady hands.

UNDERSTANDING CAMERA

LENSES

Understanding camera lenses can help add more creative control to digital photography. Choosing the right lens for the task can become a complex trade-off between cost, size, weight, lens speed and image quality. This tutorial aims to improve understanding by providing an introductory overview of concepts relating to image quality, focal length, perspective, prime vs. zoom lenses and aperture or f-number.

LENS ELEMENTS AND IMAGE QUALITY All but the simplest cameras contain lenses which are actually comprised of several ―lens elements.‖ Each of these elements directs the path of light rays to recreate the image as accurately as possible on the digital sensor. The goal is to minimize aberrations, while still utilizing the fewest and least expensive elements.

Optical aberrations occur when points in the image do not translate back onto single points after passing through the lens — causing image blurring, reduced contrast or misalignment of colors (chromatic aberration). Lenses may also suffer from uneven, radially decreasing image brightness (vignetting) or distortion. Move your mouse over each of the options below to see how these can impact image quality in extreme cases:

Any of the above problems is present to some degree with any lens. In the rest of this tutorial, when a lens is referred to as having lower optical quality than another lens, this is manifested as some combination of the above artifacts. Some of these lens artifacts may not be as objectionable as others, depending on the subject matter.

Note : For a more quantitative and technical discussion of the above topic, please see the tutorial on camera lens quality: MTF, resolution & contrast.

INFLUENCE OF LENS FOCAL LENGTH The focal length of a lens determines its angle of view, and thus also how much the subject will be magnified for a given photographic position. Wide angle lenses have short focal lengths, while telephoto lenses have longer corresponding focal lengths.

Note: The location where light rays cross is not necessarily equal to the focal length, as shown above, but is instead roughly proportional to this distance.

Required Focal Length Calculator Calculator assumes that camera is oriented such that the maximum subject dimension given by ―subject size‖ is in the camera‘s longest dimension. Calculator not intended for use in extreme macro photography. Many will say that focal length also determines the perspective of an image, but strictly speaking, perspective only changes with one‘s location relative to their subject. If one tries to fill the frame with the same subjects using both a wide angle and telephoto lens, then perspective does indeed change, because one is forced to move closer or further from their subject. For these scenarios only, the wide angle lens exaggerates or stretches perspective, whereas the telephoto lens compresses or flattens perspective. Perspective control can be a powerful compositional tool in photography, and often determines one‘s choice in focal length (when one can photograph from any position). Move your mouse over the above image to view an exaggerated perspective due to a wider angle lens. Note how the subjects within the frame remain nearly identical — therefore requiring a closer position for the wider angle lens. The relative sizes of objects change such that the distant doorway becomes smaller relative to the nearby lamps.

The following table provides an overview of what focal lengths are required to be considered a wide angle or telephoto lens, in addition to their typical uses. Please note that focal lengths listed are just rough ranges, and actual uses may vary considerably; many use telephoto lenses in distant landscapes to compress perspective, for example.

Lens Focal Length* Terminology Typical Photography Less than 21 mm Extreme Wide Angle Architecture 21-35 mm Wide Angle Landscape 35-70 mm Normal Street & Documentary 70-135 mm Medium Telephoto Portraiture 135-300+ mm Telephoto Sports, Bird & Wildlife

Note: Lens focal lengths are for 35 mm equivalent cameras. If you have a compact or digital SLR camera, then you likely have a different sensor size. To adjust the above numbers for your camera, please use the focal length converter in the tutorial on digital camera sensor sizes. Other factors may also be influenced by lens focal length. Telephoto lenses are more susceptible to camera shake since small hand movements become magnified, similar to the shakiness experience while trying to look through binoculars. Wide angle lenses are generally more resistant to flare, in part because the designers assume that the sun is more likely to be within the frame. A final consideration is that medium and telephoto lenses generally yield better optical quality for similar price ranges. FOCAL LENGTH AND HANDHELD PHOTOS The focal length of a lens may also have a significant impact on how easy it is to achieve a sharp handheld photograph. Longer focal lengths require shorter exposure times to minimize blurring caused by shaky hands. Think of this as if one were trying to hold a laser pointer steady; when shining this pointer at a nearby object its bright spot ordinarily jumps around less than for objects further away. Shaky hands rotational vibrations This is primarily because slight rotational vibrations are magnified greatly with distance, whereas if only up and down or side to side vibrations were present, the laser‘s bright spot would not change with distance.

Shaky hands vertical vibrations A common rule of thumb for estimating how fast the exposure needs to be for a given focal length is the one over focal length rule. This states that for a 35 mm camera, the exposure time needs to be at least as fast as one over the focal length in seconds. In other words, when using a 200 mm focal length on a 35 mm camera, the exposure time needs to be at least 1/200 seconds — otherwise blurring may be hard to avoid. See the tutorial on reducing camera shake with hand-held photos for more on this topic.

Keep in mind that this rule is just for rough guidance; some may be able to hand hold a shot for much longer or shorter times. For users of digital cameras with cropped sensors, one needs to convert into a 35 mm equivalent focal length. ZOOM LENSES v/s PRIME LENSES A zoom lens is one where the photographer can vary the focal length within a pre-defined range, whereas this cannot be changed with a ―prime‖ or fixed focal length lens. The primary advantage of a zoom lens is that it is easier to achieve a variety of compositions or perspectives (since lens changes are not necessary). This advantage is often critical for dynamic subject matter, such as in photojournalism and children‘s photography.

Keep in mind that using a zoom lens does not necessarily mean that one no longer has to change their position; zooms just increase flexibility. In the example below, the original position is shown along with two alternatives using a zoom lens. If a prime lens were used, then a change of composition would not have been possible without cropping the image (if a tighter composition were desirable). Similar to the example in the previous section, the change of perspective was achieved by zooming out and getting closer to the subject. Alternatively, to achieve the opposite perspective effect, one could have zoomed in and moved further from the subject.

Two Options Available with a Zoom Lens: Change of Composition Change of Perspective. Why would one intentionally restrict their options by using a prime lens? Prime lenses existed long before zoom lenses were available, and still offer many advantages over their more modern counterparts. When zoom lenses first arrived on the market, one often had to be willing to sacrifice a significant amount of optical quality. However, more recent high-end zoom lenses generally do not produce noticeably lower image quality, unless scrutinized by the trained eye (or in a very large print). The primary advantages of prime lenses are in cost, weight and speed. An inexpensive prime lens can generally provide as good (or better) image quality as a high-end zoom lens. Additionally, if only a small fraction of the focal length range is necessary for a zoom lens, then a prime lens with a similar focal length will be significantly smaller and lighter. Finally, the best prime lenses almost always offer better light- gathering ability (larger maximum aperture) than the fastest zoom lenses — often critical for low-light sports/theater photography, and when a shallow depth of field is necessary. For compact digital cameras, lenses listed with a 3X, 4X, etc. zoom designation refer to the ratio between the longest and shortest focal lengths. Therefore, a larger zoom designation does not necessarily mean that the image can be magnified any more (since that zoom may just have a wider angle of view when fully zoomed out). Additionally, digital zoom is not the same as optical zoom, as the former only enlarges the image through interpolation. Read the fine-print to ensure you are not misled. INFLUENCE OF LENS APERTURE OR F NUMBER The aperture range of a lens refers to the amount that the lens can open up or close down to let in more or less light, respectively. Apertures are listed in terms of f-numbers, which quantitatively describe relative light-gathering area (depicted below).

#Note: Aperture opening (iris) is rarely a perfect circle, due to the presence of 5-8 blade-like lens diaphragms. Note that larger aperture openings are defined to have lower f- numbers (often very confusing). These two terms are often mistakenly interchanged; the rest of this tutorial refers to lenses in terms of their aperture size. Lenses with larger apertures are also described as being ―faster,‖ because for a given ISO speed, the shutter speed can be made faster for the same exposure. Additionally, a smaller aperture means that objects can be in focus over a wider range of distance, a concept also termed the depth of field. f-# Corresponding Impact on Other Properties: Light-Gathering Area (Aperture Size) Required Shutter Speed Depth of Field Higher Smaller Slower Wider Lower Larger Faster Narrower When one is considering purchasing a lens, specifications ordinarily list the maximum (and maybe minimum) available apertures. Lenses with a greater range of aperture settings provide greater artistic flexibility, in terms of both exposure options and depth of field. The maximum aperture is perhaps the most important lens aperture specification, which is often listed on the box along with focal length(s). Canon camera lens boxes

An f-number of X may also be displayed as 1:X (instead of f/X), as shown below for the Canon 70-200 f/2.8 lens (whose box is also shown above and lists f/2.8). maximum aperture in 1:X format

Portrait and indoor sports/theater photography often requires lenses with very large maximum apertures, in order to be capable of a narrower depth of field or a faster shutter speed, respectively. The narrow depth of field in a portrait helps isolate the subject from their background. For digital SLR cameras, lenses with larger maximum apertures provide significantly brighter viewfinder images — possibly critical for night and low-light photography. These also often give faster and more accurate auto-focusing in low-light. Manual focusing is also easier because the image in the viewfinder has a narrower depth of field (thus making it more visible when objects come into or out of focus).

Typical Maximum Apertures Relative Light-Gathering Ability Typical Lens Types f/1.0 32X Fastest Available Prime Lenses (for Consumer Use) f/1.4 16X Fast Prime Lenses f/2.0 8X f/2.8 4X Fastest Zoom Lenses (for Constant Aperture) f/4.0 2X Light Weight Zoom Lenses or Extreme Telephoto Primes f/5.6 1X

Minimum apertures for lenses are generally nowhere near as important as maximum apertures. This is primarily because the minimum apertures are rarely used due to photo blurring from lens diffraction, and because these may require prohibitively long exposure times. For cases where extreme depth of field is desired, then smaller minimum aperture (larger maximum f-number) lenses allow for a wider depth of field. Finally, some zoom lenses on digital SLR and compact digital cameras often list a range of maximum aperture, because this may depend on how far one has zoomed in or out. These aperture ranges therefore refer only to the range of maximum aperture, not overall range. A range of f/2.0-3.0 would mean that the maximum available aperture gradually changes from f/2.0 (fully zoomed out) to f/3.0 (at full zoom). The primary benefit of having a zoom lens with a constant maximum aperture is that exposure settings are more predictable, regardless of focal length.

Also note that just because the maximum aperture of a lens may not be used, this does not necessarily mean that this lens is not necessary. Lenses typically have fewer aberrations when they perform the exposure stopped down one or two f-stops from their maximum aperture (such as using a setting of f/4.0 on a lens with a maximum aperture of f/2.0). This *may* therefore mean that if one wanted the best quality f/2.8 photograph, a f/2.0 or f/1.4 lens may yield higher quality than a lens with a maximum aperture of f/2.8.

Other considerations include cost, size and weight. Lenses with larger maximum apertures are typically much heavier, larger and more expensive. Size/weight may be critical for wildlife, hiking and travel photography because all of these often utilize heavier lenses, or require carrying equipment for extended periods of time.

9 THINGS YOU SHOULD KNOW ABOUT USING PRIME LENSES

1 Doors to manual Many older prime lenses won‘t autofocus on some camera bodies – the Nikon D3100 and D5100 are examples of this – which can be rather limiting for general shooting (for more, see Manual Focus: what you need to know to get sharp images). 2 High frequency Nikon‘s ring-type ultrasonic autofocus system is usually very fast, but in the brand‘s 50mm f/1.4G and f/1.8G it‘s a bit slower than you might expect. However, it‘s still fast enough for most types of shooting. 3 Bigger is better The ‗fastest‘ lenses have apertures of f/1.4 or f/1.8 and enable higher shutter speeds and reduced depth of field. This makes them more useful than f/2.8 lenses. 4 Play with light Invest in a neutral density filter if you want to shoot with large apertures – it will reduce depth of field in sunny conditions. 5 To and fro Being able to tweak the focus setting with full-time manual override is great. You can fine-tune autofocus settings without having to switch back and forth between AF and MF modes. 6 Close quarters A macro facility adds versatility, but you‘ll have to be very close to the object you‘re shooting with a 50mm lens, and a 35mm is almost unusable. 7 Open wide When shooting at the maximum aperture with fast f/1.4 lenses, outright sharpness can be a bit lacking. 8 Sitting pretty A 50mm lens on an APS-C format body is a great combination for portraiture. A maximum aperture of f/1.4 or f/1.8 enables you to blur the background much more effectively than you‘d be able to with a budget 18-55mm zoom lens.

9 Investments banking It‘s a good idea to buy a professional optic, such as an FX-compatible lens, even if you currently use an APS-C format camera. It future-proofs you in case you ever decide to trade up to a full-frame camera.

Understanding Photography ‘Circle of Confusion’

Understanding Photography Circle of Confusion A circle of confusion basically describes the smallest photographic image element that preserves details which can still be identified is an exceedingly contentious and misconstrued variable. This fluctuates with the space from the subject in main focus. A typical human eye can differentiate 5 pairs of lines per millimeter over a distance of 10 inches. The eye‘s resolving power is almost inversely relative to the distance viewed. By doubling the distance, the distinguishable line pairs are cut in half. The converse also becomes true. The normal print viewing distance is typically expressed as somewhat equal to the print‘s diagonal size. Therefore, a print that is 4×6 is typically viewed at around 7 inches however an 8×10 would most likely be observed at around 13 inches. The acquired image is normally quite a bit smaller, so it must have a much higher resolution.

The field depth is the area whereby a circle of confusion size is smaller than the human eye‘s resolution (or the medium the images is displayed upon). Circles having a diameter smaller than a circle of confusion therefore will seem in focus.

Circle of Confusion To calculate a depth of field for a camera, one must know just how big this circle of confusion may be contemplated to be in adequate focus. The acceptable maximum diameter of this type of circle of confusion typically is known as it‘s maximum allowable circle of confusion, circle of confusion limit of diameter, or circle of confusion criteria, however is frequently incorrectly called simply just circle of confusion. Out in the real world, lenses never focus every ray perfectly under even under ideal of situations, a lenses circle of confusion becomes a categorization of its optical point. The phrase circle of least confusion typically is used to describe the smallest optical point a lens can achieve, for instance by selecting a best focus location which makes a decent compromise between the changeable effective focal lengths with diverse lens zones because of spherical or supplementary aberrations. The effects of diffraction arising wave optics plus the finite lens aperture may be included in this circle of least confusion, additionally this phrase may be applied to pure ray optics. Using idealized ray optics, anywhere rays are presuppose to converge to some point when focused perfectly, the form of an un-focused point from a lens containing a circular aperture becomes a disk of light with a hard edge (sort of a hockey-puck layout as the intensity is charted as a behavior of x and y matches within the focal plane). A more generalized circle of confusion contains soft edges caused by aberrations and diffraction, and may become non-circular because of the aperture‘s diaphragm character. So the concept of diameter needs careful defining to have any meaning. The overall diameter of a minimum circle which may contain at least 90% of it‘s optical power is an acceptable definition for a diameter of a circle of confusion. Using the description of the perfect hockey-puck shape, provides an answer of around 5% less than it‘s actual diameter.

Optical Zooming Perspective change

If you photograph a subject with a tele lens and want it to have the same size on the film or sensor when photographing it with a wide angle lens, you would have to move closer to the subject. Because this would cause the perspective to change, lenses with different focal lengths are said to ―have‖ a different perspective. Note however that changing the focal length without changing the subject distance will not change perspective, as shown in the example below.

A. Scene taken with a 33mm wide angle.

B. Cropped area indicated in image A, taken with a 33mm wide angle.

C. Scene taken with 80mm tele, with the camera in the same position as in image A (same subject distance). Note that the perspective is the same as in image B, taken with a 33mm wide angle.

D. Scene taken with a 33mm wide angle after coming closer to the subjects so that the width of the two front tiles covers the width of the frame, just like in image C. The perspective is clearly different and the distance between the subjects appears larger than in image C. Images B and C show that changing the focal length while keeping the subject distance constant has—just like cropping—no effect on perspective.

Image D shows that changing the subject distance while holding the focal length constant will change perspective.

Images C and D show that a tele compresses perspective (makes subjects look closer to one another), while a wide angle exaggerates perspective (makes subjects look more separated) compared to the ‚normal‛ way we see things with the naked eye. As mentioned earlier, this change in perspective is a direct consequence of the change in subject distance and thus only an indirect consequence of the change in focal length. Indeed, a wide angle lens allows you to capture subjects from nearby, while a tele lens allows you to capture distant subjects. Perspective distortion. In photography and cinematography, perspective distortion is a warping or transformation of an object and its surrounding area that differs significantly from what the object would look like with a normal focal length, due to the relative scale of nearby and distant features. Perspective distortion is determined by the relative distances at which the image is captured and viewed, and is due to the angle of view of the image (as captured) being either wider or narrower than the angle of view at which the image is viewed, hence the apparent relative distances differing from what is expected. Related to this concept is axial magnification — the perceived depth of objects at a given magnification.

Perspective distortion takes two forms: extension distortion and compression distortion, also called wide-angle distortion and long-lens or telephoto distortion,when talking about images with the same field size. Extension or wide-angle distortion can be seen in images shot from close using a wide-angle lens (with an angle of view wider than a normal lens). Object close to the lens appears abnormally large relative to more distant objects, and distant objects appear abnormally small and hence more distant – distances are extended. Compression, long-lens, or telephoto distortion can be seen in images shot from a distant using a long focus lens or the more common telephoto sub-type (with an angle of view narrower than a normal lens). Distant objects look approximately the same size – closer objects are abnormally small, and more distant objects are abnormally large, and hence the viewer cannot discern relative distances between distant objects – distances are compressed.

Note that linear perspective changes are caused by distance, not by the lens per se – two shots of the same scene from the same distance will exhibit identical perspective geometry, regardless of lens used. However, since wide-angle lenses have a wider field of view, they are generally used from closer, while telephoto lenses have a narrower field of view and are generally used from farther away. For example, if standing at a distance so that a normal lens captures someone‘s face, a shot with a wide-angle lens or telephoto lens from the same distance will have exactly the same linear perspective geometry on the face, though the wide-angle lens may fit the entire body into the shot, while the telephoto lens captures only the nose. However, crops of these three images with the same coverage will yield the same perspective distortion – the nose will look the same in all three. Conversely, if all three lenses are used from distances such that the face fills the field, the wide-angle will be used from closer, making the nose larger compared to the rest of the photo, and the telephoto will be used from farther, making the nose smaller compared to the rest of the photo.

Outside of photography, extension distortion is familiar to many through side-view mirrors (see ―objects in mirror are closer than they appear‖) and peepholes, though these often use a fisheye lens, exhibiting different distortion. Compression distortion is most familiar in looking through binoculars or telescopes, as in telescopic sights, while a similar effect is seen in fixed-slit strip photography, notably a photo finish, where all capture is parallel to the capture, completely eliminating perspective .

THE HISTOGRAM The histogram is a graphic representation of the tonal range in a photograph, and its analysis of the image‘s tonal range provides a precise check on exposure. The histogram depicts the range of tones in an image from the darkest on the left of the graph (0 in digital terms) to the lightest on the right side (255 in digital terms).

You might think of it this way: a light meter reads the scene before you take the photo; the histogram analyzes the photo you‘ve just taken. You can choose to have the histogram appear on the camera‘s LCD along with the playback display of your photo (see your Nikon D-SLR manual for the exact procedure). That‘s what the histogram is. But why is it an important, fundamental tool of digital photography? Simply because your understanding of the histogram will tell you if it‘s necessary to adjust your exposure, and it will indicate how to make that adjustment.

The first thing to realize, though, is that it‘s not always necessary to use the histogram. In fact, selective use is best. Few if any photographers look at the histogram for each and every photo they take. In the majority of instances, your camera‘s meter will accurately and precisely set the correct exposure for the scene.

But you should check the histogram when a scene‘s lighting is especially tricky; when there are areas of deep shadow and bright light in the same scene; and when you‘re going to take a series of images in the same setting and want to be sure your exposure is right on target.

A glance at the histogram will tell you if parts of your photo are over- or underexposed. Overexposure means lack of detail in the highlights; underexposure, loss of detail in the shadows. The histogram will instantly reveal the situation: a heavy concentration at the left side of the graph means the image is underexposed and you‘ve lost detail in the shadow areas; a heavy concentration at the right means your highlights may be blown out. The remedy? You can increase your shutter speed, close down aperture or lower your ISO to correct overexposure; the opposite settings will serve to correct an underexposure.

Here‘s something you might want to use in connection with the histogram: the highlight overexposure warning. Set this option (again, see your manual for the specific activation method) and areas of overexposure will blink in the playback image. When you see these flashes of light—most people call them ―blinkies‖—you‘ll know exactly which areas of the image are overexposed. Several Nikon D-SLRs feature secondary, color histograms. Choose to display them and you‘ll see three small graphs that show the intensity of the RGB (red, green and blue) color values in the scene. If you need to adjust these values, the camera‘s white balance control is the way to do it. Some Nikon D-SLRs also allow you to magnify specific areas of the photo on playback so you can check exposure and detail rendering in very specific parts of the image. In effect, you‘re directing the histogram‘s area of analysis. The accompanying images provide examples of what we‘ve been talking about, but the best way to see exactly how the histogram can help you take control of your photography is experimentation and experience. Just go out and take pictures in a number of situations and become familiar with what the histogram can tell you about the results.

Full Frame vs Cropped Camera Sensors

Crop Factor In Cameras In digital photography, a crop factor is related to the ratio of the dimensions of a camera‘s imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference. In the case of digital cameras, the imaging device would be a digital sensor. The most commonly used definition of crop factor is the ratio of a 35 mm frame‘s diagonal (43.3 mm) to the diagonal of the image sensor in question; that is, CF=diag / diag . Given the same 3:2 aspect ratio as 35mm‘s 35mm sensor 36mm x 24mm area, this is equivalent to the ratio of heights or ratio of widths; the ratio of sensor areas is the square of the crop factor.

The crop factor is also commonly referred to as the focal length multiplier (―FLM‖) since multiplying a lens focal length by the crop factor or FLM gives the focal length of a lens that would yield the same field of view if used on the reference format. For example, a lens with a 50 mm focal length on an imaging area with a crop factor of 1.6 with respect to the reference format (usually 35 mm) will yield the same field of view that a lens with an 80 mm focal length will yield on the reference format. It is important to note that the focal length of the lens does not change by using a smaller imaging area; the field of view is correspondingly smaller because a smaller area of the image circle cast by the lens is used by the smaller imaging area Full frame cameras have been all the rage in independent level film production, but crop sensor cameras offer some huge advantages over their full frame counterparts. With the recently released crop sensor GH4 turning heads all over the indie film world, the issue is now more relevant than ever. Full frame shots undeniably look great: an ultra shallow depth of field, smooth bokeh, and a surreal almost bigger than life feeling. But along with all of these great characteristics comes compromises. For instance, a full frame DSLR has a much larger frame size than Super 35mm film, so technically the full frame look is not as true to traditional cinematography as say an APS-C sized sensor (which is much closer to the 35mm Academy standard). But there are other more practical issues as well: your lens choices on a full frame camera are quite limited and the full frame glass can get very expensive because of the overall size.

There are crop sensor cameras, like the Lumix GH4 that I mentioned at the top of this post, that have a Micro Four Thirds sized sensor, which is significantly smaller than full frame and will effectively give you a 2x crop. What this means is if you put on a 50mm lens, it will look more like a 100mm lens on your MFT camera.

The downside to this is that it can be challenging to get some specific types of shots that are relatively easy on full frame cameras. One example is the extreme wide angle (non-fisheye) shot, which would need a very specific type of wide angle lens. Luckily there are a number of MFT lenses that fit this bill, but many of them are either slow or not particularly great quality. Full Frame vs. Crop – Which To Choose If you don‘t already own a camera, then this decision can be quite a tricky one. I know that before I purchased one of my first DSLRs (well really a DSLM, the Lumix GH2), I was quite torn as to which format would suit me best. I‘m sure many of you that are gearing up to buy your first camera may find yourself in the same predicament.

It all comes down to what you are going to use the camera for. There have been absolutely gorgeous images captured with cameras across the board – full frame, MFT, APS-C, you name it. So don‘t worry about the image quality too much as part of your decision making process, because at the end of the day if the camera is in the right hands, the images will look good. Instead, focus your attention on what you as a filmmaker need. If you plan on shooting a lot of run and gun material, or documentary content, I would strongly suggest thinking about the MFT format. It‘s much easier to pull focus with and the size of the camera lends itself well to a covert shooting situation. There are some mirrorless full frame cameras out now that solve the size issue, but they are still difficult to shoot with in a guerrilla type of setting without a dedicated focus puller, so I would always recommend a more manageable sensor size for these situations.

As for full frame, these cameras are excellent for narrative storytelling in controlled environments where you have a dedicated focus puller, or can at least take time to plan your shots more strategically if you will be pulling focus yourself. They are also great if you plan on shooting a lot of low-light/streetlight footage as you can typically bump up your ISO much higher than on crop sensor cameras. Another huge advantage of full frame cameras is their ability to capture amazing stills. Even if you‘re not primarily a stills photographer, you never know when you might get asked to shoot some stills, and just about any Full Frame. camera will deliver better still photos than crop sensor cameras. After all, that is what they are intended to do. Final Thought Choose the camera that is right for you and your situation and once you‘ve made your decision – move on! Focus on lighting, composition, lensing, and all of the other elements that are far more important than your sensor size.

Get To Know Flash Photography

Flash photography isn‘t just a back-up for shooting in low-light conditions; it‘s an art form in its own right. Just because there‘s a plethora of swanky new DSLRs hitting the market with exceptionally high ISO that make it possible to shoot in virtual darkness, flash photography isn‘t dead – in fact it‘s very much alive and kicking. Although you might feel daunted by the prospect of mastering flash photography and confused by pro jargon such as rear curtain sync, flash exposure and remote triggers, it really isn‘t as complicated as it might at first seem.

In this series, we‘ll explain everything you need to know about flash photography, so you can create beautifully lit and well-crafted images in any shooting situation. Over the following pages we‘ll take you step by step through some basic flash photography techniques, before sharing a few pro secrets that will encourage you to get more creative with light.

Whether you‘re using your on-camera pop-up flash to eliminate shadows from your portraits or using a more complex multiple off- camera flash photography technique to achieve modern, arty effects, you‘ll be amazed at the difference a little flash light can make to your shots.

Get over flashgun

01 Mode selector

Much like your DSLR, most flashguns come with several modes, from manual to fully automatic, such as TTL (through the lens) metering. 02 Rotating head

The head of a flashgun can be rotated up or down, left or right. This allows you to control the direction of the light when using flash creatively – bouncing light, for example. 03 Zoom

You can use the zoom function on a flashgun to alter the spread of light. In most cases the flash will calibrate itself to the lens you have mounted on your camera. 04 Remote trigger

Some flashguns have a remote trigger function that enables you to fire more than one flashgun simultaneously. 05 Hotshoe adaptor

This is the mechanism that connects your flashgun to your camera. Ensure that it‘s locked in the correct position before you start shooting. 06 Charge light

It might take several seconds for your flash to fully recharge between your shots. Look out for the ‗fully-charged‘ light, and in some cases a beep, which will ensure your flash fires at full power for every shot you take.

Some tips for flash photography Experiment! If you‘re shooting, say, a foreground subject against a sunset or leafy background, don‘t settle for the auto settings. Vary both the ambient and flash exposure to see different effects. Shutter speed affects ambient but not flash exposure. The flash is a very brief burst occurring during the relatively longer duration of the shutter opening—a flash burst of 1/2000 sec will provide the same illumination with a shutter speed of 1/30 sec as it will with a 1/250 sec shutter. So you can lighten or darken the ambient exposure by increasing or reducing the shutter speed while maintaining the same aperture—and thus the same flash output. You can vary the shutter speed and still use autoexposure by setting the camera to aperture-priority mode. Now, when you darken or brighten with exposure compensation, the camera will vary the shutter speed but keep the aperture the same. For natural-looking fill flash, underexpose the flash exposure The idea behind natural fill is to make it look like soft ambient light. As fill flash is ordinarily used for back- or sidelit subjects, setting the flash illumination to the same level as the ambient light makes your strobe obvious. To keep it subtle, use the flash‘s exposure compensation to dial down its output. Settings in a range of –0.7 to –2 EV usually work well.

TTL flash works better with the camera in manual exposure mode By setting the ambient exposure you want manually, you eliminate one variable and can concentrate on the effects of various flash exposures, positions, etc. Say you‘re shooting a series of portraits outdoors with fill flash. You want an ambient exposure that keeps the background at a certain light level, but with the camera set to auto, it might keep adjusting this exposure as you change position, focal length, or flash output. Better to lock it in using manual mode.

With AA batteries, there is no free lunch: The batteries that give you the shortest recycling times, NiMH rechargeables, give you the fewest shots per charge; the ones that give you the most shots, disposable lithiums, have the longest recycling times. Alkaline AAs land in between.

Don‘t fear ―unnatural‖ fill. For example, a 2-stop ambient underexposure combined with full flash exposure can dramatically isolate a human figure or foreground object.

All flash photos are double exposures

The two exposures occur simultaneously, one by the ambient light, the other by the flash illumination. You can vary each of the exposures for a wide variety of different effects: You can make them of equal brightness, a little unequal, or widely unequal; you can give them different color balances; you can even vary shutter effects, with one exposure motion-blurred and the other tack-sharp. This is what makes flash photography so much fun—and so supremely useful.

Adjusting the aperture affects both ambient and flash exposure

As the aperture is the lens‘s light valve, opening it up or stopping it down will lighten or darken both exposures—provided the flash output is kept at the same level. (With the flash set to auto, it will compensate by increasing or reducing the output—more on this later.) Since a large aperture admits a lot of light, the flash can emit less for proper exposure. This will give you greater flash reach and/or longer battery life. A small aperture requires more light, and your reach and/or battery will suffer accordingly. Using a wide aperture to limit depth of field in an outdoor portrait? In bright light, this may force you to exceed your camera‘s maximum sync speed. Solution: a neutral-density (ND) filter to reduce the light entering the lens. A 6-stop (ND 1.8) filter will let you drop to 1/250 sec from 1/8000 sec, although optical viewing will be dim and autofocus dicey. For natural-looking fill flash, underexpose the flash exposure

The idea behind natural fill is to make it look like soft ambient light. As fill flash is ordinarily used for back- or sidelit subjects, setting the flash illumination to the same level as the ambient light makes your strobe obvious. To keep it subtle, use the flash‘s exposure compensation to dial down its output. Settings in a range of –0.7 to –2 EV usually work well.

Flash has color

While we think of flash as white light, flash, like all visible light, has a color cast. Accessory flash manufacturers set ―daylight balance‖ at around 5200–5500 degrees Kelvin in color temperature. This is actually a good deal warmer in color than daylight on a blue-sky day, when color temperature can go as high as 10,000 degrees K (very blue), leading to a mismatch in color balance. This is why digital cameras have separate presets for flash and daylight white balance.

A more common mismatch: flash with tungsten room light. With a digital camera set to flash white balance, the foreground subject will appear a neutral color while background illumination out of the range of the flash will have a yellow-red cast. (Many photographers like this look and set it up deliberately.) Flip the camera‘s white balance to tungsten, and the background light will shift to neutral while the foreground subject appears very blue. Want to even the balance? Put an amber filter over the flash lens, and set the camera to tungsten or auto white balance.

With film, you may need to add an extra step to color balancing. Shooting daylight film under fluorescent lights, you would put a green gel (CC 30) over the flash head to balance it with the greenish fluorescents. You‘d then place a magenta filter (such as the Tiffen FL- D) over the camera lens to neutralize the now-overall green cast. Autoflash varies the duration of the flash Modern accessory flash units automate exposure by reading the bounce back of the flash through the lens (TTL). (Many units now make this reading via a brief preflash.) The camera/flash brain adjusts the flash exposure by making the burst shorter or longer for less or more light, respectively. The range of flash bursts is pretty astounding—a typical accessory unit may have durations from 1/1000 sec to 1/50,000 sec or even less. You also adjust manual flash power by changing duration, almost always measured in fractions: full power, 1/2, 1/4, 1/8, etc., often down to 1/64 power for the shortest flash duration.

Use very brief flash durations for extreme motion-stopping photos. Positioning the flash close to your subject, using a wide aperture, and setting a high ISO will all shorten the duration of autoflash, and you can dial in high speed manually, too. Keep the ambient light and/or ambient exposure low, though, or you might just capture a ghost—the term for ambient motion blur in a flash shot. Flash follows the same hardness/softness rules as ambient light

The broader the light source, the softer the light. That‘s why studio portraits shooters use softboxes, umbrellas, and beauty dishes on their strobes. But the narrower the light source, the harder the light. So studio shooters use snoots and grids to get hard, even harsh, effects. Placing the light source closer to your subject makes it broader and therefore softer; moving the light source farther away makes it narrower and harder. Flash falls off in proportion to the square of the distance

The beam from a flash unit is cone-shaped—shoot a relatively close object and most, if not all, of the light cone will cover it. As you move farther away, though, a smaller portion of the light cone hits the subject, as more of the light sprays wide. At a great enough distance, the flash‘s light becomes imperceptible to the eye as well as to a sensor or film. And it‘s a square relationship: If you move twice as far away from your subject, you get only 1/4 the illumination on the subject; triple your distance, and you get only 1/9 the light. Setting the zoom head of an accessory flash to tele position will create a narrower cone, but you lose wide-angle coverage. Yet just because you‘re far from your subject doesn‘t mean your flash has to be. You can position an accessory unit close to your subject and fire from a distance via a wireless trigger.