[sane-devel] Digital ICE support

[Nils Philippsen]

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
nils@tiptoe.de / nphilipp@redhat.com / nils@lisas.de
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Ever noticed that common sense isn't really all that common?