Hubert Figuiere said: > On lun, 2003-12-01 at 09:42, Nils Philippsen wrote: > >> > > You mean e.g. not giving up on Kodak slides? I have many of this >> type, >> > > so I'll love to have it as well. >> > >> > I assume you mean Kodachrome? I think it's possible to do IR cleaning >> >> Yes. >> >> > on Kodachrome, but it's a lot harder than for E6 and C41 because the >> > IR channel is more strongly correlated with other colours than in the >> > case of E6/C41. >> >> From my (small) experience, it's only harder with Kodachrome, the other >> slides I had (mostly Agfa consumer material) had almost perfect IR >> channels with no resemblance to the original picture, only speckles and >> scratches. > > The problem with Kodachrome is the same as it is with B&W negative film. > The sensitive emulsion contains a large amount of silver and this > materiel does produce something when scanning with IR, unlike it is done > with conventionnal C41 or E6 emulsions. > > Nikon has apparently solved the problem with the latest Coolscans, but > one has to investigate how.
As I said, the "ghost images" in the IR channel of Kodachrome slides have all been less intense than real defects. This should be solvable, my first try (with a fixed, experimentally determined threshold) looked rather promising. The obstacle is always finding the right threshold to discriminate between defects and ghost images, I think this (function) should also be made dependent on whether we assume the scan in question to be a difficult or an easy one (determining this by e.g. amount of "light" pixels in IR channel). Nils -- Nils Philippsen / Berliner Straße 39 / D-71229 Leonberg // +49.7152.209647 n...@tiptoe.de / nphil...@redhat.com / n...@lisas.de PGP fingerprint: C4A8 9474 5C4C ADE3 2B8F 656D 47D8 9B65 6951 3011 Ever noticed that common sense isn't really all that common?
