Archived posting to the Leica Users Group, 2001/07/25
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Johnny Deadman writes: > In the case in question, as Austin points out, > it is perfectly possible to position the sensors > so you get a uniform gray. Easier said than done. The sensors would have to be positioned with perfect precision, which would require a very contrived test, unlike anything that happens in the real world. It would be equivalent to sampling a sine wave at precisely the points where it crosses zero. And the sampling frequency must be _identical_ to the target frequency, otherwise a uniform gray will not be the result. All this has drifted quite a bit from the original point, though, which was that 53 lp/mm is entirely adequate for most 35mm photographs (which rarely get beyond 40 lp/mm), and that it is also quite achievable with a 2700-dpi scanner. So drum scanning at 16000 dpi will generally buy virtually nothing in terms of increased image quality. A 4000-dpi scan results in a very modest improvement, and any more beyond that doesn't really change anything at all.