U of S | Mailing List Archive | alt-photo-process-l | Re: curves and gum and Christopher James book

Re: curves and gum and Christopher James book

Hello Yves,

The only thing we want with printed negatives is to make them 'behave' in such a way that the image tones in the final print are exactly as the image tones onscreen. This is the same as in the wet darkroom where contrast and density are carefully controlled to get a negative that is capable to print maximum black and pure white and translates image tones in a way that fits your printing technique.
In making digital negatives there are several ways to arrive (in the print) at what you see onscreen. We discussed them at lenght and many excellent methods are refined every day and available on the web. All digital negative approaches are translating image tones to negative UV density to get final printtones that correspond with the onscreen image. They do it in different ways though: some use color to block UV and some control inkdensity or combinations of both. Each density in the file is then translated, linearized, by a curve, to control UV density and behaviour in the negative.

This curving approach differs from a printing aproach with icc profiles. If you map onscreen tones to printtones, as we do for our own processes, equipment and workflow, there's no big need for a simulation onscreen. As you look at Sandy's prints for example you can see he both masters the printing techniques he uses as the translation from his onscreen image tones to print tones. I'm shure his onscreen image looks perfect too.

Saying, if I understand you right, that the onscreen image does not look nice with the correction curve applied, or with some kind of printsimulation curve as you suggest, makes absolutely no sense. A correction curve is an intermediate step to get a good negative. What's wrong with that. It's a minor step compared to the long way we go to get an alt print. If you care to look into the QuadToneRip approach you will also learn that it's possible to put all the curving into the RIP (that only costs a 50 dollar shareware fee) and leave your onscreen image untouched.

Apart from that it is imaganable to use an icc profiled workflow. But to get a good profile for each technique is maybe more complicated then the curving approach. A downloaded icc profile of somebody else's workflow will never work very well for you because of all the 'personal variables'. The nice thing of doing it yourself 'the hard way' is that you understand the relation between digital image tones, inks and substrates and the caracteristiques of your lightsensitive material. And all that at very low cost.


On 11 mrt 2008, at 07:59, Yves Gauvreau wrote:


Lets say we want to simulate what a print of some image would look like on screen. A print that would have been made with a strait PDN or RNP negative of course. One simplistic way to do this would be to use a strait line "curve" where you change point(0,0) to say point(0,15) and point(255,255) to say point(255,233). Now, I would believe not many of you would like this new on screen image.

The question that come to my mind is why a print that transformes your original in a very similar fashion as above become something that everyone seems happy about? Do you all accept these limitations as part of doing alt-prints?