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Re: Epson or HP for alt-phot ... ? (some OT)
> > There are problems with using full range. ... physical problem... tone
> > mapping... gamma ...
>
> I am not so sure about this. I have determined the amount of ink to
> give maximumn white.
Hi Jeff,
Sorry that I wasn't writing ning myself clearly. What I meant was for the
original scan not to use the full range from 0 to 255. In particular, avoid
the very low value (especially 0). This is in conjuction with the
consideration of monitor calibration.
For the output itself, of course you can use curve to give you any value that
gives you the desired black and white.
> I may not use the gamma function as I may use a set of curves to correct
> for contrast adjustments. But I will keep the "0 problem" in mind.
You should at least give it a try. Mmm.... I read some schematics from your
web site, so it looks like you are engineering/technically oriented, so I
will just briefly say that the gamma function is a power function. If you
take the log of the power function, the log values are linear. The original
digital values correspond to intensity, so the progression (in terms of
density) is also log. Therefore, the gamma function is acting exactly like
zone compression or expansion.
So you can calibrate for a "normal" negative, then if your negative is
flatter or contrastier, just do a gamma adjust and things will still fall
properly.
> A major difference is that I am doing all adjustment and control in CMYK
> not RGB. (The first thing I do is convert the scanned RGB into CYMK.)
What I meant is basically the digital value (0 to 255). In either case, try
to avoid 0.
Dave Soemarko
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