Friday, January 19, 2007
Photoshop Week Part 3: HDR
HDR stands for High Dynamic Range, an increase in the range between the dark areas and light areas in a photo.
While your eye can see a pretty wide range between dark and light, and switch very quickly between the two, you camera cannot. A photographer must choose what part of the picture is important, and expose accordingly. This will leave the rest of the picture either blown out and overexposed or dark, detailess and underexposed.
Except that now we have software, Photomatix Pro, that can create an image with a much broader range, called an HDR picture. It can do this in one of two ways, the first and best is too combine multiple exposures into one 'super exposure.' This is like the three pictues I started with, though notice that Photomatix still had to do some enhancement as I didnt have a wide enough range of exposures to really do the scene justice. I was simply bracketing, looking for one good exposure, not trying to capture all the range in the scene for on HDR.
While combining images usually makes for the best quality HDR, it has its problems. For one thing you had better have a nice, super stable tripod. If it moves even a little bit, on just one of your 3-7 exposures, then your work is for naught, as I have found out with many of my recent multiple exposures! I may have to see about buying a better tripod, but I'm afraid costs seem to ramp up very quickly.
Luckily there is another way, Photomatix can also generate an HDR image from a single RAW file, the uncompressed, usually quite large and unwieldy image file taken by your digital camera. This can require a fair amount of enhancement though, and that results in noise. Notice below, the remarkable difference in the city scene, but also notice the severe digital noise cluttering up the enhanced portion. Had I had a series of exposures to mesh into one, that noise would have (hopefully) been reduced a bit.
HDR's also offer up a lot of opportunities for crazy manipulation in Photoshop. While even I don't always appreciate an overly processed image, I have to admit that many of these 'more real than real' pictures can be very compelling. They may not be a replacement for regular photographs, but they are a great addition to the family. To see some really crazy HDR's, check out the blog that first introduced me to the concept, Stuck in Customs. But might I note that he has a much better camera than I... ;-)
While I won't be changing to an all HDR format anytime soon, its pretty time and effort intensive, I'll certainly be posting many more as the year wears on and I get a chance to experiment a bit more. Enjoy!