I'm working my way through Camera Raw by Bruce Fraser and there is a lot to learn from this book and not all about RAW either:
"With digital, you need to turn the old rule upside down - you need to expose for the highlights, and develop for the shadows!" - Page 21
I had sensed this almost as soon as I began shooting digital, but didn't have a clear understanding of why:
Digital cameras record photons in direct proportion to how many photons strike the sensor. It is called a linear gamma. So you get a lot of bits describing the higher tonal values, but the human eye doesn't see the same way a sensor does, and can't make out these small differences in the highlights. But us humans are very sensitive to slight changes in the darker areas.
When you darken the image, you are forcing more bits into the lower values - and this is moving them from the higher values where they don't make much of a difference (you can't pick up all this white info with your eye). Here is the confusing part though. So if the eye can make out more in the darker areas, wouldn't it make sense to expose for the darker areas? No. And the reason, as best as I understand it, is what happens next. You take the image and you are going to use level sliders or RAW controls to darken the image. When you do this, you will be pushing the historgram to the right, i.e. knocking off some white information - so you want to make sure that you still have enough white bits to describe the highlights.
2) RAW is about as close as you get to a "digital negative." Any sort of editing you do, you are going to lose information. So it is not only that you are shooting RAW that is important, but that certain types of adjustments are made in the RAW will also give you more information to use when you do go to Photoshop adjustments.
I'm about a third of the way through the book, although there are some sections that I go back to, but that was $34 well spent. My plan for the day is to continue experiments with the Photoshop RAW module, and to see what differences I can pick up in prints.
Get Info on Amazon: Camera Raw by Bruce Fraser (buy through this link and you help me with my digital education).
One of the first things I want to see is if I can see a difference in a black and white print between an 8-bit and an 16-bit grayscale image.