fup2 rec.photo.digital

Floyd L. Davidson:

The actual distinctions between file formats are
embedded in the files, not the name. For major
differences, for example to indicate that a file is from
Canon, Pentax, Nikon, or whatever, the first few bytes
of the file are an indicator. That is referred to as a
"magic number", and is true of most unique file formats
(JPEG, .exe, TIFF, .dvi, .gz and so on all start with a
"magic number" to identify them uniquely).

"Uniquely" - in theory. To make things more complicated, some formats
get reused. As an example, Nikon's NEF (at least the variant I got) is
in fact a TIFF file with some private tags. When you open a 20 MB NEF
file with a regular image viewer that ignores file extensions (as it
should) and doesn't know about NEF (like ACDSee 3), all that is
displayed is the tiny RGB preview image.

However, people handling Nikon RAW files usually know what to do with
them anyway, so I wouldn't consider that a huge problem. If the file
extensions get lost and the person responsible for handling the files
doesn't know about their origin, it might become a problem, though.