HDR (high dynamic range) photography is a relatively new technique in the world of still photography. Every photographic scene that we encounter has a range of brightness...a contrast range. The contrast range is the range of luminosity from the brightest highlights to the deepest shadows. The problem for the photographer is the camera's inability to record detail across the whole range of brightness when photographing a high contrast scene. HDR attempts and if done properly will enable the photographer to produce a single image that reproduces detail across the entire range of contrast by combining different exposures of the same subject into a single file. In the past an elaborate lighting setup may have been used to lighten the shadows, reducing the contrast range, so that details are visible in the entire photo. Now the same result can be achieved without the lights. In future posts I will get more specific but in general here is what we're doing. When faced with a high contrast scene we are taking several exposures at varying exposure settings making sure that across our exposure set we have recorded detail in all areas of the scene. That is, we have proper exposure of the highlights, mid tones, and shadows for the same exact shot across at least 3 exposures. The exposures are then combined digitally (there are many photo editing programs out there that can do this) to produce a single file with highly visible detail in all elements of the image. Let's look at the example above of the railroad cars. Three exposures were combined to produce this image. Notice that there is good detail throughout...the sky is blue, the rust in the tracks is highly visible, and even the inside of that front wheel is full of detail. The range of contrast in this scene is unrecordable by todays digital cameras (in a single exposure, that is). In order to get that detail in the wheel in one exposure the photographer would normally have to blow out the highlights...to keep the sky blue she would have to let some shadows go black. There are several steps involved in the hdr process (none of which is that complicated) and in future posts I will address them. For now let's be aware that contrasty scenes that used to be beyond the latitude of film, or beyond the ability of a digital sensor to capture, can now be recorded in several exposures and combined to produce a single image with good detail throughout the range.
