I find one of the big differences of digital photography as compared to film is the reduced dynamic range of digital cameras. This image of a field bike repair was taken at the Leslie Spit. Notice the bright sunlight reflecting off the cement. I am not happy with the light and dark contrast in the above image.
If the image is too bright to the point that one or more of the color channels are clipped/pegged at its maximum value (which is 1024 for the canon rebel xt). Then areas that are brighter then this max value will lose all of the details. The image on the left has had the brightness increased by 25%.
On the other hand if the image is too dark then the dynamic range of image is reduced and fine detail is lost. Some of the detail can be brought back by digitally enhancing the image in a program like Photo Shop. This is especially true if you are working in raw mode. But fine detail is still lost and noise especially in the dark areas will be increasingly visible. There is a mathamatical basis beyond the scope of this post for this increase in noise and lose of detail.
The answer to getting better contrast is simple but too late for this time around. It was pointed out to me after the fact that I should have used flash fill-in to bring out the dark areas. I knew about flash fill-in but always thought it was used in lower light situations. In general I stay away from using the flash as I usually get glare off a sweating nose or forehead, but in bright sunlight glare shouldn't be a problem. Oh well another reason to buy a remote flash.