Archived posting to the Leica Users Group, 2001/07/24[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
> > From: Austin Franklin [mailto:firstname.lastname@example.org] > > > > > The recent POP Photo scanner review *measured* the resolution of > > > the LS-4000 at 60 lp/mm. As I understand it, noise plays a major > > > role in reducing the true resolution of a scanner down from the > > > theoretical resolution (which would be 78 lp/mm for a 4000 SPI > > > sensor). > > > > I'd have to think about that, but that does not make sense > > (noise limiting > > the resolution) to me. Noise certainly does limit the > > dynamic range (which > > is on a per pixel basis), but I fail to see how it limits the > > resolution, > > which would be across pixels. If the lense is not up to snuff, or the > > scanner has vibration issues, I can see that limiting > > resolution...but not > > noise. > > I agree that electrical noise in the CCD would reduce dynamic > range, not resolution. Something is lowering the resolution, > though (if Pop Photo is to be believed :-) Could one culprit be > the scanning lens itself? After all, the light doesn't go > straight from the LED to the sensor. What about scattering in > the film and emulsion itself? And bloom, and vibration. In all > liklihood there are a large number of factors contributing to the > degradation, just like there are with any other real-world process. CCD red channels are typically "soft", because of smear, not bloom. Smear is like cross-talk, bloom is like clipping. That is probably the reason. I wish they would test the channels independently...as well as some come out with a scanner that scans B&W NOT in RGB... My scanner scans B&W using a single ND filter, but it's the only scanner I know of that has been designed that way.