U of S | Mailing List Archive | alt-photo-process-l | Re: Two tricolor prints

Re: Two tricolor prints


Part of the problem is that I posted to the wrong thread regarding your curve.

I believe it was your post below that I was referring to.  It sounded as if the curve you had calibrated for gum was giving you flat midtones in order to get separation in the shadows and highlights—as were examples that others had sent to you.

I was asking if you could send the curve you were working on or post it so that I could see more clearly what you are talking about—often the shape of the curve will tell you a lot about what is going on.

Best Wishes,
Mark Nelson

Precision Digital Negatives - The System
PDNPrint Forum at Yahoo Groups

In a message dated 9/26/07 10:54:34 AM, kthayer@pacifier.com writes:

Yes, but the overall low contrast is to some extent an inevitable 
result of setting the density of the negative to match the scale of 
the gum, which was part of my point.  There's so much difference to 
be made up that it's very difficult to find a curve that will replace 
the contrast that you've lost, if that makes sense.    If you have 
any slope through the midtones, then you sacrifice separation in the 
highlights or shadows or both.  If you get separation in the 
highlights and shadows, then your midtones have to be flat.   So 
far,  I haven't found a curve that makes a better gum print than a 
diagonal line does (for my printer, light, negative media, etc) but I 
haven't given up yet.

I would think maybe I was missing something (which is entirely 
possible, since while I'm generally thought of as a fairly 
intelligent person and mastered statistics with no trouble, this 
stuff just makes no sense to me at all) except that a number of 
people have thoughtfully sent me calibration charts and curves to 
show me how I "should" be calibrating my curves for gum, and these 
have shown the same difficulty I'm struggling with.   For one thing 
they have been made with underpigmented mixes, which I find 
interesting and somewhat inexplicable, but the main thing is that the 
post-curve step tablets seem to follow the same pattern:  say in a 
101-step chart, the steps from 1-10 or so show nice gradation, and 
the steps from 85 or 90 to 100 show good gradation, but all the steps 
from 15-85 are the same tone.  And the curve reflects that exactly: a 
slope in the highlights and shadows, but horizontal through the 
midtones.  Or, they have to lighten the highlights too much in order 
to leave room for a slope in the midtones.  No matter what you do, 
something has to give.   So I'm still struggling with that 
fundamental difficulty with making curves for gum.

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