Re. 2D scanners for autoradiographs and the like - be aware that although
camera responses are supposed to be linear with intensity this is
often not the case in practice, particularly at the extremes of brightness
and darkness levels. Also watch out for cameras that automatically
adjust the gain and offset - then output depends critically on the
average brightness of the image, so if you move the gel or autoradiograph
or have additional bands or whatever the results would change. Good
software/hardware packages will "know" about and cater for these problems
but when you buy you should know how they are being handled in the system
you have. Think also about the need for "internal" standards in gels when
you want to quantitate amount of label in particular bands etc. I haven't
done this kind of work myself (although Ive done image processing based
quantitation type stuff), so these are merely the things I would look out for
as a prospective buyer (in addition to the other stuff mentioned by others).
Cheers, Paul Fisher.