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High Dynamic Range Photography HDR comparison photos. HDR is “High Dynamic Range” photography. Read the following paragraphs for information about HDR photography. I am thrilled with the results of using HDR software, so I am including these comparison photos so you can see the value of using HDR photography. Some of the HDR photos have increased noise and other issues, because I have a lot to learn about settings for the HDR software. The comparison photos may include:
What is HDR photography? Cameras can’t see the range of light intensity that our eyes can, and monitors can’t display the range of light intensity that our eyes can see. This results in many photos having dark shadows and/or washed out skies. HDR photography is the process of taking several photographs of a scene at various exposure levels, then merging the images into one file, with a high range of light intensity. Each image contributes important information about the scene, such as details in the shadows or details in the sky. After merging the images, the next step in the process is to convert the file to a range that we can view and print. This second step is called tone mapping. Multiple photos must be of the exact same scene. If anything moves, such as trees, people, or vehicles, the final image will have undesirable “ghosting”. If you can’t control movement of objects in the scene, then the HDR image may have to be made from one image. This results in an image with a smaller range of light intensity, but tone mapping may produce a better image than without using the HDR process. Exposure Value (EV) is the same as “stop”, and refers to half or double the amount of light. When a digital camera saves an image in RAW format, the image will have about 10EV, or a medium dynamic range. When the image is saved in JPEG format, the image will have about 8EV, or a low dynamic range. Outdoor sunlight has 17EV, so you can see that more than one image must be made, to capture that range of EV. The HDR format has the capacity to represent the full range of brightness in the scene. Tone mapping then compresses this high dynamic range image to a low dynamic range that we can view on monitors and printers. This is an excellent resource book for HDR photography: Complete Guide to High Dynamic Range Digital Photography, by Ferrell McCollough; Published by Lark Books, a Division of Sterling Publishing Co. ISBN-10: 1-60059-196-5 ISBN-13: 978-1-60059-196-9 The analogy used by the above book, for understanding tone mapping, is to think of a spring (dynamic range) that is too large to fit into a box (the range of a monitor or printer). When the spring is sufficiently compressed, it will fit into the box. As stated above, the HDR process begins with taking several photographs of a scene at various exposure levels. If the camera is handheld, the camera must be capable of auto exposure bracketing (AEB). If your camera is not capable of AEB, you will need a tripod. The object is to take several photos, with different settings, without moving the camera. Pictures for HDR photos must be taken in manual exposure and aperture-priority modes. Only the shutter speed will be varied (by the camera if using auto exposure bracketing). Ideal camera setup:
See the referenced book for much more information. This web page is my listing of information in the above book, so I can find the information faster. Thank you for Bob Lott and his HDR presentation to the Chester County Camera Club, for getting me started on using HDR photography.
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