Image values reside only in the midtone-to-black range, "hitting" the black-point "wall"|
Exposure mistakes in digital imaging only favor one direction: under exposure. If a file is underexposed, the values and information containing the detail of the image are mostly there, it is just compressed. We like to refer to such an image as being only "mostly dead."
If, however, the file is overexposed, and especially has "hit the white-point wall," we affectionately refer to that as "all Dead!" There is not much that can be done with it. The detail and information beyond the white point has all been converted to pure white, and is therefore lacking in any detail - for good.
There is one way to save your back, however, but must be done before the shoot: Shoot in Raw format, or in what Kodak claims is just as good, ERI JPEG (only supported by Kodak, and a format we have never rewiewed). RAW captures the images exactly as the chip records the scene, and still contains highlight detail and information.
Most Photographers daily debate if they will use the RAW format, it does provide all power, but in inconvenient. Click here for more info on the pro's and con's of the RAW format, and all formats.
JPEG is often the preferred format for busy photographers. It is compact, writes and reads faster, and if you shot correctly, it captures an almost lossless image at a quarter to one eighth the size!
The problem is that it sets in stone the exposure, white balance, and colorspace of the image. This tutorial assumes that you must have an image in either TIFF, JPEG, or PSD; and therefore need to correct for exposure, white balance, and colorspace.
I have other pages that will discuss how to correct for exposure, the Color Balance section reviews correcting white balance, and the Color Management Workflow Tutorial covers the choices in colorspaces.