Re: green-yellow
That's interesting Clay -- and thank you. I observed this "grain" effect too when printing out the RNP Arrays. But it never dawned on me that similar contrasting ink carts would produce smoother highlight tones. A nice bit on info and a compelling reason to use QTR. I think I know, but for the record which did you start pairing together? The magenta pairs and the cyans pairs? I just learn to observe the "problem" areas on my colour tests and then avoid using the grainy "paths" as choices for negative colours. To answer Loris' question : it's a wavelength filter effect pure and simple. Certain coloured negatives will absorb emitted light better than others colors. It's a dance between the light source colour and the negative colour. The proof of this can be had comparing exposures made in the UV box compared to the light from the Sun, then compare this to a tungsten source. UV is on the "blue" side of the colour spectrum. What kind of filter do you use in BW photography to make your sky go dark? Yellow or Green will turn a blue sky from dark to black. ~m Clay wrote: FWIW, it is very instructive to print out the QTR ink limits test and graph the UV transmission density versus ink percentage for each ink on a single graph. When I did this for my printers, the 'aha' moment came when I realized that certain combinations of ink colors are going to be more prone to the graininess effect that is sometimes observed in the highlight areas of prints. In particular, the green color that I used for a long time combines two colors that are very far apart in terms of UV transmission density at a given density: i.e. the yellow and cyan inks. When I constructed profiles using only ink combinations that are close in terms of UV transmission density, I got some of the smoothest highlight transitions ever.
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