To expand on this point:
The primary purpose of sharpening (unsharp mask) is to compensate for the diffusion that occurs as various papers absorb ink in the printing process. Printing on newsprint requires more sharpening than is needed when printing on a glossy stock. In this regard, it is needed just as much for film as for digital.
Of course some digital cameras don't produce totally sharp images out of camera and thus benefit from some sharpening. But the same thing could have been done to slightly blurred film images if you have the technology. (Now you can scan the film and sharpen it.)
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Anytime you are talking about papers absorbing ink, you are usually dealing with a halftone process, and the relative need for sharpening according to ink spread or the effects of the halftone process are intimately linked. As mentioned previously, sharpening is not ordinarily used when printing film with an enlarger onto photographic paper.
If you scan film, then sharpening is needed to compensate for loss of sharpness during the scanning process, even if the original negative was perfectly sharp.
It is useful to separate sharpening into two phases: capture and output. With scanned film and digital captures, the capture sharpening compensates for loss of sharpness introduced during capture. For output, differing amounts of sharpening are needed according to the media and resolution. Also, more sharpening is needed for halftone than contone output.
Of course, if the negative is not in focus or there is blurring from motion, one could apply an unsharp mask when printing on photographic paper with an enlarger. Or one could scan the negative and sharpen it with an unsharp mask. However, in the latter case the use of a deconvolution method of sharpening may give better results, especially in the case of motion blur.
Bill