I’m back from teaching a workshop in Bryce and Zion, and a question came up that happens a lot…clipping a specific channel. Many folks use a cumulative histogram when checking exposure, meaning the histogram uses red, blue and green channels to come up with an average result. This works…most of the time. But when a specific channel is clipped, for instance the red channel when photographing large expanses of sandstone, the averaged histogram shows no clipping. But the RGB histogram will show the clipped channel. Do I really need to worry about this? Yes, especially if the clipped area is a major part of your subject.
If you clip, or over expose, any one channel, then you will lose that information at capture and won’t be able to magically make it reappear. You can move some sliders in CS6 or LR4 to try and bring it back, but only a little piece.
Here is another example. I was recently in Cambodia, and wanted to capture a monk in one of the old temples. I had to shoot at -1.7 exposure comp. to prevent the robe from blowing out. When you try to print something blownout, the colors block up and look muddled. So the next time you see a strong color in your image, use the RGB histogram and keep those channels from clipping!