Digital cameras record a remarkable amount of information about each exposure. This is often called EXIF data (EXIF is actually one of several formats for recording it), and Windows itself, as well as many software packages, can read the EXIF data in JPEG files. Photoshop and other utilities can read the same kind of data in raw files. From this book's Web site (www.dslrbook.com) you can get a utility, EXIFLOG, that reads a set of digital image files and generates a list of exposures.
This fact gives you an incentive to do two things. First, keep the internal clock-calendar of your camera set correctly. Second, take each exposure as both raw and JPEG if your camera offers that option. That way, each exposure is recorded as two files that serve as backups of each other, and the JPEG file contains EXIF data that is easy to view.
The original Digital Rebel (EOS 300D) always records a small JPEG file with the .THM extension alongside every raw (.CRW) file. If you rename the .THM file to be .JPEG, your software can read the EXIF data in it.
Naturally, the camera doesn't record what it doesn't know. It can't record the focal length or f -ratio of a lens that doesn't interface with the camera's electronics. Nor does it know what object you're photographing or other particulars of the setup and conditions. Nonetheless, using EXIF data saves you a lot of effort. You don't have to write in the logbook every time you take a picture.
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Although we usually tend to think of the digital camera as the best thing since sliced bread, there are both pros and cons with its use. Nothing is available on the market that does not have both a good and a bad side, but the key is to weigh the good against the bad in order to come up with the best of both worlds.