Get to Know Your Lenses
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Estimation and Correction of the Distortion in Forensic Image Due to Rotation of the Photo Camera
Master Thesis Electrical Engineering February 2018 Master Thesis Electrical Engineering with emphasis on Signal Processing February 2018 Estimation and Correction of the Distortion in Forensic Image due to Rotation of the Photo Camera Sathwika Bavikadi Venkata Bharath Botta Department of Applied Signal Processing Blekinge Institute of Technology SE–371 79 Karlskrona, Sweden This thesis is submitted to the Department of Applied Signal Processing at Blekinge Institute of Technology in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering with Emphasis on Signal Processing. Contact Information: Author(s): Sathwika Bavikadi E-mail: [email protected] Venkata Bharath Botta E-mail: [email protected] Supervisor: Irina Gertsovich University Examiner: Dr. Sven Johansson Department of Applied Signal Processing Internet : www.bth.se Blekinge Institute of Technology Phone : +46 455 38 50 00 SE–371 79 Karlskrona, Sweden Fax : +46 455 38 50 57 Abstract Images, unlike text, represent an effective and natural communica- tion media for humans, due to their immediacy and the easy way to understand the image content. Shape recognition and pattern recog- nition are one of the most important tasks in the image processing. Crime scene photographs should always be in focus and there should be always be a ruler be present, this will allow the investigators the ability to resize the image to accurately reconstruct the scene. There- fore, the camera must be on a grounded platform such as tripod. Due to the rotation of the camera around the camera center there exist the distortion in the image which must be minimized. -
With Its Focal Length Shorter Than That of the Normal Lens, the Wideangle Lenses Cover an Angle of View of 60° Or More. The
With its focal length shorter than that of the normal lens, the wideangle lenses cover an angle of view of 60° or more. The wideangle lens allows coverage of quite a broad view from a close camera position or photography in constricted areas. It can be effectively utilized in architectural exteriors and interiors and group shots. The wideangle lens is also suited for instant candid work which does not allow precise focusing on fast-moving subjects. Its profound depth of field compensates for inaccurate focusing. Another outstanding feature of the wideangle lens is exaggeration of perspective. This type of lens tends to give an interesting and dramatic effect which is more conspicuous, the wider the angle of lens. Today, "Wideangle Shooting" occupies a unique place in creative photography. Advanced photographers often emphasize the exaggerated perspective known as "wideangle distortion" to accomplish special creative effects. Nikon offers one of the widest selections of outstanding wideangle lenses to meet specific photographic requirements in wide field photography. L-15 20mm f/3.5 Nikl<or-UD Auto Code No. 108-01-105 The concept of optical construction is entirely new. Focal length: 20mm The lens consists of 11 elements in 9 groups, with Maximum aperture: 1 : 3.5 Lens construction: 11 elements in 9 groups back focus 1.87 times longer than the focal length. Picture angle: 94° Thus, the lens can be mounted on the camera with Distance scale: Graduated both in meters and feet up to the mirror in normal viewing position. (There is no 0.3m and 1ft f/3.5 - f / 22 need to lock up the mirror.) Aperture scale: Aperture diaphragm: Fully automatic With this lens, there is almost no need to focus, if Meter coupling prong: Integrated (fully open exposure metering) the diaphragm is closed down slightly. -
Depth of Field in Photography
Instructor: N. David King Page 1 DEPTH OF FIELD IN PHOTOGRAPHY Handout for Photography Students N. David King, Instructor WWWHAT IS DDDEPTH OF FFFIELD ??? Photographers generally have to deal with one of two main optical issues for any given photograph: Motion (relative to the film plane) and Depth of Field. This handout is about Depth of Field. But what is it? Depth of Field is a major compositional tool used by photographers to direct attention to specific areas of a print or, at the other extreme, to allow the viewer’s eye to travel in focus over the entire print’s surface, as it appears to do in reality. Here are two example images. Depth of Field Examples Shallow Depth of Field Deep Depth of Field using wide aperture using small aperture and close focal distance and greater focal distance Depth of Field in PhotogPhotography:raphy: Student Handout © N. DavDavidid King 2004, Rev 2010 Instructor: N. David King Page 2 SSSURPRISE !!! The first image (the garden flowers on the left) was shot IIITTT’’’S AAALL AN ILLUSION with a wide aperture and is focused on the flower closest to the viewer. The second image (on the right) was shot with a smaller aperture and is focused on a yellow flower near the rear of that group of flowers. Though it looks as if we are really increasing the area that is in focus from the first image to the second, that apparent increase is actually an optical illusion. In the second image there is still only one plane where the lens is critically focused. -
The Trade-Off Between Image Resolution and Field of View: the Influence of Lens Selection
The Trade-off between Image Resolution and Field of View: the Influence of Lens Selection “I want a lens that can cover the whole parking lot and I want to be able to read a license plate.” Sound familiar? As a manufacturer of wide angle lenses, Theia Technologies is frequently asked if we have a product that allows the user to do both of these things simultaneously. And the answer is ‘it depends’. It depends on several variables - the resolution you start with from the camera, how far away the subject is from the lens, and the field of view of the lens. But keeping the first two variables constant, the impact of the lens field of view becomes clear. One of the important factors to consider when designing video surveillance installations is the trade-off between lens field of view and image resolution. Image Resolution versus Field of View One important, but often neglected consideration in video surveillance systems design is the trade-off between image resolution and field of view. With any given combination of camera and lens the native resolution from the camera is spread over the entire field of view of the lens, determining pixel density and image resolution. The wider the resolution is spread, the lower the pixel density, the lower the image resolution or image detail. The images below, taken with the same camera from the same distance away, illustrate this trade-off. The widest field of view allows you to cover the widest area but does not allow you to see high detail, while the narrowest field of view permits capture of high detail at the expense of wide area coverage. -
A Guide to Smartphone Astrophotography National Aeronautics and Space Administration
National Aeronautics and Space Administration A Guide to Smartphone Astrophotography National Aeronautics and Space Administration A Guide to Smartphone Astrophotography A Guide to Smartphone Astrophotography Dr. Sten Odenwald NASA Space Science Education Consortium Goddard Space Flight Center Greenbelt, Maryland Cover designs and editing by Abbey Interrante Cover illustrations Front: Aurora (Elizabeth Macdonald), moon (Spencer Collins), star trails (Donald Noor), Orion nebula (Christian Harris), solar eclipse (Christopher Jones), Milky Way (Shun-Chia Yang), satellite streaks (Stanislav Kaniansky),sunspot (Michael Seeboerger-Weichselbaum),sun dogs (Billy Heather). Back: Milky Way (Gabriel Clark) Two front cover designs are provided with this book. To conserve toner, begin document printing with the second cover. This product is supported by NASA under cooperative agreement number NNH15ZDA004C. [1] Table of Contents Introduction.................................................................................................................................................... 5 How to use this book ..................................................................................................................................... 9 1.0 Light Pollution ....................................................................................................................................... 12 2.0 Cameras ................................................................................................................................................ -
Choosing Digital Camera Lenses Ron Patterson, Carbon County Ag/4-H Agent Stephen Sagers, Tooele County 4-H Agent
June 2012 4H/Photography/2012-04pr Choosing Digital Camera Lenses Ron Patterson, Carbon County Ag/4-H Agent Stephen Sagers, Tooele County 4-H Agent the picture, such as wide angle, normal angle and Lenses may be the most critical component of the telescopic view. camera. The lens on a camera is a series of precision-shaped pieces of glass that, when placed together, can manipulate light and change the appearance of an image. Some cameras have removable lenses (interchangeable lenses) while other cameras have permanent lenses (fixed lenses). Fixed-lens cameras are limited in their versatility, but are generally much less expensive than a camera body with several potentially expensive lenses. (The cost for interchangeable lenses can range from $1-200 for standard lenses to $10,000 or more for high quality, professional lenses.) In addition, fixed-lens cameras are typically smaller and easier to pack around on sightseeing or recreational trips. Those who wish to become involved in fine art, fashion, portrait, landscape, or wildlife photography, would be wise to become familiar with the various types of lenses serious photographers use. The following discussion is mostly about interchangeable-lens cameras. However, understanding the concepts will help in understanding fixed-lens cameras as well. Figures 1 & 2. Figure 1 shows this camera at its minimum Lens Terms focal length of 4.7mm, while Figure 2 shows the110mm maximum focal length. While the discussion on lenses can become quite technical there are some terms that need to be Focal length refers to the distance from the optical understood to grasp basic optical concepts—focal center of the lens to the image sensor. -
LENSES There Is Something Magical About the Image Formed by a Lens
LENSES There is something magical about the image formed by a lens. Surely every serious photographer stands in awe of this miraculous device, which approaches ultimate perfection. A fine lens is evidence of a most advanced technology and craft. We must come to know intuitively what our lenses and other equipment will do for us, and how to use them. ~ Ansel Adams LENSES A pinhole is the simplest way to form an image. A pinhole creates a very soft focused, diffused image that is often aesthetically pleasing. Pinhole cameras can be very complex or very simple in construction. ~ Ansel Adams LENSES Focal Length When choosing a camera you must also choose the appropriate lens for whatever subject matter you will be photographing. Lenses come in a wide variety, not only in focal length but also in price. Purchasing the right lens can be difficult if you don’t understand some basic terminology: Focal Length is what gives lenses their names (wide, telephoto, zoom, etc). The focal length is defined as a distance from the center of such a convex element (principle point) to the focal point (image plane) and it is one of the most decisive factors that determines the characteristics of a lens. When purchasing a lens we recognize the focal length of the lens sometimes by its physical length, but mainly by the number designated. For example: 50mm, 85mm, 200mm, 70-200mm, etc. The focal length is usually the first decision to make in purchasing a lens. Focal Length LENSES One of the greatest advantages to purchasing a digital SLR camera is the fact that you can purchase a wide variety of lens for every purpose. -
Notes on View Camera Geometry∗
Notes on View Camera Geometry∗ Robert E. Wheeler May 8, 2003 c 1997-2001 by Robert E. Wheeler, all rights reserved. ∗ 1 Contents 1 Desargues’s Theorem 4 2 The Gaussian Lens Equation 6 3 Thick lenses 8 4 Pivot Points 9 5 Determining the lens tilt 10 5.1Usingdistancesandangles...................... 10 5.2Usingbackfocus........................... 12 5.3Wheeler’srules............................ 13 5.4LensMovement............................ 14 5.5BackTilts............................... 14 6Depthoffield for parallel planes 15 6.1NearDOFlimit............................ 15 6.2FarDOFlimit............................ 17 6.3DOF.................................. 17 6.4Circlesofconfusion.......................... 18 6.5DOFandformat........................... 19 6.6TheDOFequation.......................... 19 6.7Hyperfocaldistance......................... 20 6.8Approximations............................ 21 6.9Focusgivennearandfarlimits................... 21 6.9.1 Objectdistances....................... 21 6.9.2 Imagedistances........................ 22 7Depthoffield, depth of focus 23 8Fuzzyimages 24 9Effects of diffractiononDOF 26 9.1Theory................................. 26 9.2Data.................................. 27 9.3Resolution............................... 29 9.4Formatconsiderations........................ 31 9.5Minimumaperture.......................... 32 9.6Theoreticalcurves.......................... 33 10 Depth of field for a tilted lens 35 10.1NearandfarDOFequations.................... 35 10.2 Near and far DOF equations in terms of ρ ............ -
The Camera Versus the Human Eye
The Camera Versus the Human Eye Nov 17, 2012 ∙ Roger Cicala This article was originally published as a blog. Permission was granted by Roger Cicala to re‐ publish the article on the CTI website. It is an excellent article for those police departments considering the use of cameras. This article started after I followed an online discussion about whether a 35mm or a 50mm lens on a full frame camera gives the equivalent field of view to normal human vision. This particular discussion immediately delved into the optical physics of the eye as a camera and lens — an understandable comparison since the eye consists of a front element (the cornea), an aperture ring (the iris and pupil), a lens, and a sensor (the retina). Despite all the impressive mathematics thrown back and forth regarding the optical physics of the eyeball, the discussion didn’t quite seem to make sense logically, so I did a lot of reading of my own on the topic. There won’t be any direct benefit from this article that will let you run out and take better photographs, but you might find it interesting. You may also find it incredibly boring, so I’ll give you my conclusion first, in the form of two quotes from Garry Winogrand: A photograph is the illusion of a literal description of how the camera ‘saw’ a piece of time and space. Photography is not about the thing photographed. It is about how that thing looks photographed. Basically in doing all this research about how the human eye is like a camera, what I really learned is how human vision is not like a photograph. -
Tutorials: Depth of Field
TUTORIALS: DEPTH OF FIELD Ed. Note: Information presented by Steve Fowler – 10/15/14 Camera Club Meeting Depth of field refers to the range of distance that appears acceptably sharp. It varies depending on camera type, aperture and focusing distance, although print size and viewing distance can also influence our perception of depth of field. This tutorial is designed to give a better intuitive and technical understanding for photography, and provides a depth of field calculator to show how it varies with your camera settings. The depth of field does not abruptly change from sharp to unsharp, but instead occurs as a gradual transition. In fact, everything immediately in front of or in back of the focusing distance begins to lose sharpness — even if this is not perceived by our eyes or by the resolution of the camera. CIRCLE OF CONFUSION Since there is no critical point of transition, a more rigorous term called the "circle of confusion" is used to define how much a point needs to be blurred in order to be perceived as unsharp. When the circle of confusion becomes perceptible to our eyes, this region is said to be outside the depth of field and thus no longer "acceptably sharp." The circle of confusion above has been exaggerated for clarity; in reality this would be only a tiny fraction of the camera sensor's area. When does the circle of confusion become perceptible to our eyes? An acceptably sharp circle of confusion is loosely defined as one which would go unnoticed when enlarged to a standard 8x10 inch print, and observed from a standard viewing distance of about 1 foot. -
DEPTH of FIELD Depth of Field Is Simply the Area in Front of Your Camera Where Everything Looks Sharp and in Focus
DEPTH OF FIELD Depth of field is simply the area in front of your camera where everything looks sharp and in focus. For example, if you're focused on somebody standing 10 feet in front of the camera, your depth of field might be from 8 feet to 14 feet. That means objects falling within that area will be Large Aperture = Less Depth Of Field acceptably-sharp and in focus; objects falling outside the area will be soft and out of focus. DEPTH OF FIELD Small Aperture = Greater Depth Of Field Next: Your depth of field increases as your subject gets farther from the camera. The farther away the subject, the more depth of field; the closer the subject, the less depth of field. There are several important things to know about depth of field. First is this: Your depth of field decreases as you increase your focal Length. In other words, with a Disatant Subject = Greater Depth of Field telephoto lens you have a much shallower area in focus than with a normal lens. That's why with a zoom lens, you zoom in to telephoto for focusing--it makes it easier to see the exact point where your subject is sharpest. Close Subject = Less Depth of Field Finally: You always have less depth of field in front of Telephoto = Less depth of field your point of focus than behind it. This is especially noticeable at distances of 25 feet or less. At these near The next thing to know is: Your depth of field increases distances, you can usually figure on your depth of field as you decrease your focal length. -
141 Midterm Review
141 midterm review FILM EXPOSURE Short or Wide-angle Lenses Exposure is controlled by: 1. Common wide angle lenses for a 4x5 1. f/stop (or aperture) located in the lens view camera: 90mm and 75 mm 2. Shutter speed. The shutter is: 2. Give a wider angle of view than a normal lens. a. located in the camera body on a 3. Have more depth of field than longer lenses. 35mm single-lens reflex 4. Increased feeling of space. b. located in the lens on a 4x5 view camera The B setting holds the shutter open for as long as Long or Telephoto Lenses: the shutter release is held. 1. Common long lenses for a 4x5: 210mm, 300mm The X setting on the shutter is for electronic flash 2. Give a narrow angle of view. synchronization, M is for flash bulbs. 3. Are generally slower than wide lenses. The T setting is for long exposures. Pressing the 4. Less depth of field than shorter lenses. shutter once on T opens the shutter, 5. Compress space. pressing it again closes the shutter. DEPTH OF FIELD- The area of the image Equivalent exposures are adjustments made to in front and back point of focus, that falls within shutter speeds or f/stops which change a visual acceptable focus. effect without altering film or print density. Example: Depth of field (DOF) is determined by: changing from f8 at 1/125 to f11 at 1/60, increases 1. F/stop (smaller apertures increase DOF) the depth of field in the scene while maintaining an i.e.