Re: self masking and POP

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From: Sandy King (sanking@CLEMSON.EDU)
Date: 02/03/03-10:25:01 AM Z


Judy Seigel wrote:

>
>As I understand it, that's a THEORY, and I think it may well be invalid,
>and since it has all kinds of ramifications, I wanted to test it. I
>realized later that I should have tested two different sections of
>different colors, to see if say a red held back more light than the
>blue... because that was what interested me. I'll do it next week.

And it is not my theory, though I tend to think it may well be valid
because blue indeed offers less actinic filtration than other colors.
In three-color carbon printing, for example, printing speed is always
much faster with the cyan record than with the magenta (next fastest)
and yellow (slowest) records.

>
>As for "self masking" -- from what you say it's impossible to test that so
>we can say anything we please. Well, I shall say that there is no self
>masking and how will you prove that there is?

  I actually tried to figure a way to do this with carbon some weeks
ago because Dick Sullivan offered the opinion, perhaps on another
list, that the print-out image that results from conversion of
dichromate to chromate, even in the absence of pigment, should lead
to some self-masking in carbon. I don't believe that is correct
because of the almost linear response of a carbon curve that you see,
in practice. However, to this point I have not been able to figure
out a good test for self-masking in carbon.

> After all, you can't simply
>compare it to another process, because every process has a different
>contrast range. And also and therefore the range of every process
>(including and especially every paper combo with a particular procedure
>and chemistry) has to be tested separately. So what is the meaning in
>this context of any *theory* at all? Suppose, if we must have theory, that
>I have a theory that cyanotype makes you more beautiful than otherwise.
>There are all kinds of reasons for that but it's now 4:21 AM & my bedtime.

Yes, it is true that every process has a certain contrast range,
although this can usually be modified significantly. However, from a
practical perspective we know that certain things are true of DOP
processes as opposed to POP processes. With a DOP process you will
loose either the highlights or the shadows, depending on amount of
exposure, unless the contrast of the negative is carefully matched to
the exposure scale of the paper. Assume, for example, that you try to
print with a negative that has a higher density range than the ES of
the paper. If you print for good shadow detail the highlights will
have no texture, whereas if you print for good highlight details the
shadows will block up completely and go completely black. And of
course I mean a straight print, with no dodging, burning. With a POP
process you can print the entire tonal scale of the negative, even
when the density range of the negative is much longer than the
exposure scale of the process, *but* by the time you managed to get
good detail in the highlights you will start to lose contrast in the
shadows because of self-masking, and the overall contrast of the
print will be significantly reduced. The result of this is that the
print will loose overall contrast but the shadows will never go
completely dark.

Sandy King

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