Understanding Exposure – Aperture, Shutter Speed, and ISO Copyright © 2014 Nature Photography Simplified All Rights Reserved If you like the content of the eBook, feel free to share this link with your friends and family members http://www.naturephotographysimplified.com/free-ebook-15-incredible- bird-photography-tips-beginners/ This is for your Personal Use only. Please do not alter any of its content. Thanks for your understanding. www.naturephotographysimplified.com http://www.naturephotographysimplified.com Page 2 Understanding Exposure – Aperture, Shutter Speed, and ISO Photography Basics – Understanding Exposure, Aperture, Shutter Speed, and ISO Many photographers think that understanding Exposure is the toughest aspect in photography. Several people may shy away from a DSLR because they have to understand some of the alien terms like Aperture, Shutter Speed, ISO, etc. The reality is that understanding these key concepts is easy and fun. It requires a bit more time and patience to understand it in depth. Aperture, Shutter Speed and ISO are the basic building blocks of photography. If you understand how each of them work together to get an optimal exposure, you will enjoy your photography to the fullest. To make the camera see the way we see is the most difficult aspect in photography. But, as we understand more about the exposure, we will be able to make the camera see what we want it to see. We all know that we see the world through our eyes with the help of light. When there is absolutely no light, then we do not see anything. In a way, our eyes are exposed to light to form a picture in our brain through which we perceive/understand our world. A photograph is made when the lens (or eyes) bends the light onto the sensor (or brain) to form a photograph (or picture). Exposure Exposure, in simple terms, means how much time the camera sensor is exposedto the light to make a photograph. The amount of light passing through the lens opening (Aperture) for a specified duration of time (Shutter Speed) for which the camera sensor is open is called the Exposure. http://www.naturephotographysimplified.com Page 3 Understanding Exposure – Aperture, Shutter Speed, and ISO Exposure is essentially a combination of Aperture, Shutter Speed, and ISO. To keep the matters simple, let us concentrate only on Aperture and Shutter Speed and keep the ISO for later articles. Here is a simple equation for exposure: Exposure = Aperture + Shutter Speed + ISO We will go through each of these core concepts Aperture, Shutter Speed, and ISO in detail in the upcoming articles. A properly exposed photograph will contain proper color information and all the details that are present in the actual scene. A photographer’s life is so much easier in today’s digital world due to histograms. You can see if the exposure is correct or not by looking at the histograms. However, the knowledge of exposure will enable you to achieve optimum exposures to fulfill the artistic needs and to achieve creative results. Underexposure If the amount of light passing through the lens opening for duration of time when the camera sensor is open is less than optimal, then it is called underexposure. The underexposed photograph will look darker than the real scene. Underexposed photographs usually lack details in the shadow regions resulting in the crushed blacks. The histogram of such photographs, show the distribution towards the left most side with some clipped blacks. http://www.naturephotographysimplified.com Page 4 Understanding Exposure – Aperture, Shutter Speed, and ISO This photograph of a Great Egret is severely underexposed throwing the background very dark. We see crushed blacks in several parts of the photograph. The histogram shows the clipped blacks indicating an underexposed photograph Overexposure If the amount of light passing through the lens opening for duration of time when the camera sensor is open is more than optimal, then it is called overexposure. The overexposed photograph will look brighter than the real scene. Overexposed photographs usually lack details in the highlight regions resulting in the washed out details. The histogram of such photographs, show the distribution towards the right most side with some clipped whites. http://www.naturephotographysimplified.com Page 5 Understanding Exposure – Aperture, Shutter Speed, and ISO This photograph of a Chipmunk is overexposed as well as underexposed portions. Upper right half of the background is completely overexposed showing no details. Histogram shows the clipped highlights in the right hand side of the graph Optimal Exposure If the photograph looks closer to reality, then the exposure is optimal. As photographers we may decide to either expose and develop the photograph to depict the reality or to depict our artistic vision. The Belted Kingfisher photograph has the optimum exposure. This is also indicated with the nice distribution of the histogram without any clipping on either end http://www.naturephotographysimplified.com Page 6 Understanding Exposure – Aperture, Shutter Speed, and ISO Exposure Range or Dynamic Range Every camera possesses an exposure range or dynamic range that depicts its capability to collect the light information. This light information is later converted to a suitable form to represent a photograph. In simple terms, an exposure or dynamic range is nothing but the lowest and the highest exposure a camera can record in a given scene. Or the darkest and the brightest details a camera can record in a given scene. Dynamic range may vary from camera to camera based on how much light the sensor can hold. The larger the sensor and its pixel size, greater the dynamic range, since it can capture higher amount of light. For example, consider a camera that has 5-stops dynamic range. Suppose, the main subject needs an aperture of f/11 (with constant shutter speed of 1/125th of a second), then everything in the scene that requires an aperture of f/5.6 to f/22 will be represented properly. Anything below f/5.6 will result in pure black and anything above f/22 will result in pure white. Note: The Shutter Speed and ISO are assumed to be constant Let us understand the dynamic range using Shutter Speed instead. Suppose, the main subject needs a shutter speed of 1/125th of a second (with constant aperture say f/11), then everything in the scene that requires a shutter speed of 1/30th to 1/500th of a second will be represented properly. http://www.naturephotographysimplified.com Page 7 Understanding Exposure – Aperture, Shutter Speed, and ISO Anything below 1/30th of a second will result in pure black and anything above 1/500th of a second will result in pure white. Note: The Aperture and ISO are assumed to be constant I have considered a 2-stop lower and 2-stop higher than the normal for the sake of explanation. In reality, the film cameras (or negatives) usually tend to preserve more details in the brighter regions than the darker regions. The digital cameras tend to preserve more details in the darker regions than the brighter regions. http://www.naturephotographysimplified.com Page 8 Understanding Exposure – Aperture, Shutter Speed, and ISO How to achieve optimum Exposure for different scenes Let us examine how we can find the optimum exposure for various scenarios that we encounter on day to day basis. How to Achieve Optimum Exposure for a High-key Scene A high-key scene contains lower dynamic range than a good consumer/pro camera can handle. There will be a uniform distribution of light in the high-key scene. Foggy, rainy and cloudy days usually lead to high-key scene since most of the scene will be equally lit. High-key scene usually contains the uniform lighting, yielding to lower Dynamic Range Consider our 5-stop dynamic range camera for example. Assume that we are photographing a waterfall on a cloudy day. It is a well distributed light and mostly the scene is having two dominant colors, white and green. If you meter the waterfalls, then the metering may indicate an f/11 as in our example study. So, we have a dynamic range of f/5.6 to f/22. But as you know, waterfall is the brightest element in the entire scene. There is no subject/object at f/16 and f/22. However, we would have lot of details in the green area or the surroundings. If the shadow regions need a smaller aperture than f/5.6, you will have those region turn to black. If you happen to expose the scene with f/11 aperture, then you would end up with a darker or an underexposed image. http://www.naturephotographysimplified.com Page 9 Understanding Exposure – Aperture, Shutter Speed, and ISO This is the time, when you have to make a decision as a photographer to utilize the opportunity to come up with an optimum exposure. Misty morning scene in Blue Ridge Parkway yields to a high key lighting. The histogram shows that the dynamic range of the entire scene is limited and can be captured easily. Note that I have exposed the scene to the right of the histogram If you decide to expose the waterfalls at f/5.6 by using exposure compensation of +2, then you will get a 4-stop dynamic range (f/2.8 to f/8) to represent the shadow region or the surrounding. This technique is also called as ETTR (Expose To The Right). In this process, we are opening up the aperture by 2 stops and allowing more light to pass through the lens. http://www.naturephotographysimplified.com Page 10 Understanding Exposure – Aperture, Shutter Speed, and ISO This way you will have a virtually greater dynamic range to represent the entire region in a much more pleasing way leading to an optimum exposure.