Re: Minolta 5400 or Coolscan V

On Tue, 12 Jul 2005 22:20:43 +0100, Kennedy McEwen
<rkm@xxxxxxxxxxxxxxxxxx> wrote:

>>However - it is my understanding - that a conventional light source
>>doesn't have the same problems with Kodachromes as Nikons do. Is that
>>wrong?
>>
>Yes, it is wrong. There is no intrinsic reason why a LED source should
>be any more susceptible to Kodachrome problems than a white light
>source.

Actually, I find the confirmation it was only a misunderstanding quite
reassuring! This clarification removes the last nagging feeling (and
it was only a feeling) about LEDs that I (for one) had.

If the conventional light source doesn't intrinsically (!) make any
difference to Kodachromes that makes the LED choice the perfect one!

Especially after you debunked the other, equally wrong, urban legend
about LEDs somehow causing the narrow DOF of Nikon scanners.

>>In other words, does a conventional light source Kodachrome scan
>>suffer from the notorious "blue cast" as well?
>>
>That is a completely different issue.
>
>A colour cast is simply a white balance error. You need a different
>white balance for KC with a LED scanner because the dyes have a
>different spectral characteristic from the typical E-6 dyes and you are
>measuring the colour at three specific wavelengths rather than averaging
>across 3 wide and overlapping ranges of wavelengths. This is just
>metamerism - the same effect that makes certain coloured material look
>different under light sources with different spectral characteristics.

That was one of the first things I picked up in this group way back!

Indeed, it was your reference to a partially painted car which during
the day looked perfect in the shop, but parked outside under street
lighting clearly showed every spot touched up in the shop.

On reflection, it makes perfect sense. What we see is what bounces off
the object. If, however, the light we throw at the object is limited
in some way, then what bounces off will also be limited the same way.

>If you want to see just how different the spectral dye density and
>characteristic curves typically are between KC and E6 films, take a look
>at the three graphs in these pdf files:
>http://wwwuk.kodak.com/global/en/consumer/products/pdf/e88.pdf
>http://www.kodak.com/eknec/documents/a9/0900688a80316ba9/e126e.pdf
>
>In particular, note just how different the characteristic curves are in
>the shadows - the densest dye on KC is red, on E6 it is blue - so colour
>balance in shadows will be different between these films irrespective of
>the light source. However, also look at how different those spectral
>dye density curves are as well! Interestingly, Kodak have put a section
>that specifically deals with these issues on the page before the curves
>of the Elite Chrome link.

By a coincidence (and after the other thread about characteristic
curves) I just downloaded a bunch of them from Kodak the other day!

Thanks once again, Kennedy, for throwing... erm... light (sic) on the
subject by... erm... reflecting (sic) on this! ;o)

Don.
.

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