Reading a few articles last night, people seem confused over the definition of ‘High Dynamic Range’ photography. Basically, Photoshop and other programs have tools that allow you to combine several different exposures into one composite picture, with more contrast in areas that were previously under or over exposed, for a very cool brightening effect. So the argument is whether you can use a single exposure to create an ‘HDR’ image, and some people feel strongly that by definition this is not HDR. The counter argument usually mentions that most Camera RAW formats store a larger dynamic range than what can be displayed on a typical monitor or LCD; however people don’t seem to understand the significance of this fact.
My argument comes after a sunset bracketing session this weekend in Stockholm. These days, after setting the shutter speed and aperture, the CCD output on a digital SLR is interpreted by software in the camera. Since we control shutter speed, aperture, and ISO on the camera, when you think about it ISO is just software interpretation that the camera uses to raise or lower values the CCD captured. So for bracketing you can change any of these three, but often you want a certain aperture or shutter speed for the circumstances. Since these two values only change the optics the CCD is exposed to, the rest is all software, which I would always prefer to leave for post processing (including white balance, color temp etc) as much as possible, as this is the major advantage in saving RAW data.
Beyond the optics of a given image, it seems everything is controlled by software; the digital CCD has an optimal operation range that the camera understands, and in general you will get the best dynamic range from your CCD using camera presets. You can always get a little more range by using the composite of several pictures, but do they have to originate from physically different images? I say this is irrelevant; a lot of the data is already controlled by software; if you want to combine two optically different images that makes sense, but otherwise it doesn’t matter how your dynamic range is achieved, if the result enhances your shot the way you want. That’s the advantage in shooting RAW; you can do a lot with a single image. Anyone who argues otherwise is lacking experience, and of course the proof is in the pudding. Thanks to Mike Kennedy and John Slemp for helping me understand all of these factors, and showing me so many great examples. I guess I’d better go update my gallery now, just as soon as I finish processing this single sunset shot over Stockholm.
