Introduction to High Dynamic Range Photography
If you’ve been photographing for any length of time, you’ve probably discovered that what you see is not always what your camera delivers. Shadows become black blobs. Light areas become glaring spaces of pure white.
Even the best camera cannot see the way the human eye sees. Your eyes are capable of detecting about 10,000 levels of light from total black to total white.
Your digital camera, on the other hand, can only record a small fraction of that total. Your odds of capturing a high contrast scene are equally small without finding some way to even the playing field.
In the analog era of film, solutions to the sight/camera discrepancy ranged from complex exposure and development systems to using graduated neutral density filters to even out the tones in a photographed scene. But with the advent of sophisticated digital technology, photos can now be manipulated with image editing software to capture a range of tones that heretofore was the sole domain of the human eye.
Merging photos with High Dynamic Range software
High Dynamic Range (HDR) software merges photographs of differing exposures into a single image. Typically, though not exclusively, three images are used: one is underexposed (dark), one is normal exposure, and one is overexposed (bright).
Each photo contains details that the others lack. Once merged the resulting photo contains all the detail.
You can either manually adjust a series of exposures or use your camera’s built-in exposure bracketing function (not available on all point and shoots) to capture three or more photos of a single scene at different exposure values. You then import the series of photos into the HDR software to combine them into a single image with an expanded range of tones, which then can be manipulated for color, contrast and sharpness.
HDR photography is actually a two-step process as the HDR video tutorial at the end of this article illustrates. The HDR file is created by merging several images in the HDR software. The resulting image contains a range of tones that cannot be displayed on a computer monitor. Those tones must be compressed, or tone mapped, before the photograph can be viewed or printed.
Tone mapping an HDR image involves mapping the data from the high dynamic range image into one with a lower dynamic range by saving it in a JPEG or TIFF file format. After an image is mapped, you can do additional editing with the new image.
Many a debate has been waged in photography forums as to the value of overly tone mapped images. That debate is likely never to end as long as individual tastes vary.
Most high-end photo imaging software packages, such as Lightroom and Photoshop Creative Suite, feature HDR functionality.
Photomatix Pro is available as a free download from hdrsoft.com. The program is a full version, but generates a watermark over the final image. To disable the watermarking function, a key code can be purchased from Hdrsoft. The free download allows you to experiment to determine if HDR photography is for you before purchasing the key code or investing in a high-end software package.
While most HDR software packages boast of their ability to align photographs taken while holding the camera by hand, the best results will be achieved with the use of a tripod to steady the camera between shots. It is also possible to process a single RAW image file into several images of varying exposure values.
Some newer digital cameras now include an HDR mode that combines multiple exposures.
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