Originally Posted by
Bruce Watson
Most consumer and prosumer flatbed scanners can't read the extreme density end of color positive films. It's difficult to do with flatbeds in general because of light scattering from adjacent pixels which you can't get away from in scan-a-line-at-a-time scanners. Most drum scanners, OTOH, can come sufficiently close, in large part because they are lighting just the one pixel at a time and thus controlling the lighting considerably better than a flatbed can.
While the Dmax of color positive films does normally (that is, almost always) exceed the Dmax of color negative and B&W negatives, it does not follow that the scanner hardware is under utilized when scanning negatives. This might be true for consumer and prosumer flatbeds. But it's certainly not true for most drum scanners, and I think for most professional flatbeds. Drum scanners in particular let the operator set the log amps right were the operator wants them, so the black and white points are exactly what the operator wants -- the scanner is neither underutilized nor over utilized. What that means is, you can make an exact match between the density range of the film and the digital range of the scanner. So if your scanner is good for, say, 14 bits of range, and your film density runs from 0.3 to 1.2, you can apply the 14 digital bits of range to cover exactly the 0.9 density range of the film. Hard to pull more tonality out of a film than that. Just sayin'.
That, and there's a lot more going on in scanning B&W negatives than just density. How you make that density has a lot to do with how the scanner can perform. Said another way, there's a large difference between scanning dye clouds and scanning metallic silver grain clumps.
There was a time I thought this was true too. For a short while I reasoned that I should be developing B&W film to even higher densities for scanning, reasoning like you seem to be that "the hardware can handle it". But it turned out, the *film* can't handle that. And when scanned on a drum scanner, even though the scanner could handle it, the resulting scans were... awful? Because they faithfully reproduced how I had abused the film. My favorite film artifact was density waves at high contrast edges; looked sorta like ripples in a pond. Kodak had a name for that, but I've forgotten what they called it. Sigh... it was a long time ago.
So... I started lowering Dmax to see if there even was an optimum. It turned out there was. But it was different for different work flows. Just like finding your PEI, or your "N" development time. So you have to tune your workflow to get the most out of it. No big secret, this.
What I found was, with my camera, lenses, meter, film, developer, processing, scanner, software is that I got optimal results by keeping my Dmax about 1 to 1-1/2 stops lower down from where I would have wanted it to print in the darkroom. So... Dmax around 1.0.
Now the question is, why? And the answer isn't the density itself. It's how the density is created. Silver grain clumps are not translucent like dye clouds are. They reflect light. That is, light scatter. That is, Callier Effect. Just like you get in a darkroom enlarger. Scanners see this too.
So... what do I mean by "optimal results"? Same as the Zone System -- easy to print. When I optimized my negatives for scanning, I could actually, on occasion, make straight prints. I was never able to do this in darkroom printing. Never. But with this optimal-for-scanning workflow I came up with, I could make excellent prints (on occasion, I want to emphasis that again) that needed no dodging, burning, or other manipulation. It was eerie. It was cool. It saved a lot of time and work. And it looked better. Really worked well in the print.
After a lot more research I figured out why. Basically, I reduced Callier Effect sufficiently that my photographs were not experiencing much if any highlight compression. Highlight compression is one of the ways Callier Effect manifests itself. The light scattering from the highlight density of the negative tends to "contaminate" the dark areas by making them lighter, like a fog. When this is minimized, you don't have to fix the highlights in the print.
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But... you (anyone reading this, not just SergeyT) don't have to believe me. In fact, I'd be shocked if anyone did. It's easy enough to do your own testing find out what actually works for you and how you do things. Find the truth by doing the work. Evaluate. Come back here and tell this thread (or start a new thread) what you found. Just as I have now told you what I found. Information sharing is what this place is about -- we all want to learn from each other to improve our work.
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