Profiling film recorder
Profiling film recorder
- Subject: Profiling film recorder
- From: email@hidden (Scott Kilbourne)
- Date: Tue, 08 May 2001 16:54:15 -0400
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Hi Group!
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I have this service bureau that makes slides for me but
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they don't really know too much about all this (their prices
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are good thoug).
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How would I go about profiling their machine so that I can
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get a fair softproof of what their setup would output.
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If the machine for exposing slides from data doesn4t use laser to write
the information direct into the emulsion it works like this ( and most
of the machines on the market do because it s cheaper):
a fine light-point writes the data on a high resolution monochrome CRT (
8000 lines or more ). The film will be exposed by this light-point three
times through a red, green and blue filter and a classic reproduction
lens with a 135mm, middle-format or large-format-back. And this is the
mistake in the system. Because of the CRT and the lens the slides never
can be as sharp as laser-written slides. The CRT has no black matrix so
the bright point doesn4t illuminate only one of the 8000x8000 possibly
"pixels" but also "wastes" the field arround it because it has an
unsharp corona. When You try to give out an TC2.0 RGB Testchart You will
see that there are bright patches in the neighbourhood of dark patches
and these dark patches get wasted by the corona of the bright ones. Even
when the slide machine exposes correctly these "wasted" patches will be
measured as too bright !
The other problem is that the emulsion of analog films doesn4t react
linear like other digital output systems. You cannot linearize it. When
Your profile tries to correct the file for the slide machine You cannot
be sure if the emulsion reacts like it should.
What You can try to do is to test different emulsions like Kodak EPP,
Kodak electronic output-film, Agfa RSX.
The "best" results at all even with profiling I got with Kodak EPP.
And You can try to take the TC 2.0 and sort the patches new and make a
new reference data but this is a weekend job I started 2 years ago and
interrupted because from time to time I have to earn some money ;-) )
and want to play with my kids ;-). For all this You need a Gretag
Spectrolino with SpectroscanT - XY-reader or similar machines. But to
get one exposed 44x54slide measured ( smaller transparencies You cannot
handle)
You need about 1 1/2 hours and don4t make a mistake !
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A couple comments on the above. High quality film recorders such as the Solitaire
above will accept downloaded lookup tables to adjust the imaging characteristics
such as gamma, color balance, etc. One problem with profiling film recorders is
that it is very difficult to read small color test patches on 35mm film which
measures 24x36mm image area. Some test programs to linearize film recorders shoot
many frames of film for each test with relatively large targets.
If anyone knows of SW (and the hardware...) to create ICC profiles of 35mm slides,
I'd love to hear about it.
-Scott