That was in the other recent topic. 
I coincidentally saw a different mention of the same silver vs. dye difference only a couple hours before this post. It was in a short blog post linked here, where you are mentioned by name, hehe. That was the first time I remember seeing the phrase “chromogenic monochrome” used as a description to mean “not using silver particles”.
So I might be making a machine that is better for silver-based film when I don’t actually have any of that to scan (save for the calibration target itself). It would be a more realistic test in this early stage to have some of that SMPTE test film (on chromogenic monochrome film!) than continuing to use this laser-etched, silver-coated glass USAF 1951 target.
I don’t think I understood what you meant here. Do you mean that by choosing to allow a reduction in contrast it’s possible to relax many of the requirements of the hardware so the time between starting to build a machine and when it’s able to produce a meaningful result is shorter? (I would agree with that!)
That’s an interesting notion that it might be possible to use the “highest contrast” aperture with all those over-sharpening artifacts and simply post-process it down to something nice. We have so much compute available these days that it’s kind of ridiculous.
Like I’d mentioned in the other thread, I’m not particularly interested in the grain. I’m hoping that when I reach the wet-gate stage near the end of this journey, it’ll have the same muting effect as shown in Fig.24 of the “Film Grain, Resolution and Fundamental Film Particles” paper you linked there.
Rather than going for grain structure, my goal is to get as much of the original picture signal by maxing out each of these parameters (best focus for each channel, ideal contrast, eventual wet-gate, etc.). I’m reasonably sure that this 1936x1464 sensor is going to be able to sample all the frequencies I’m looking for.
Taking a step back, my reason for all of these experiments is because my instinct is telling me there is a good 10-15% of something being left on the table by the usual RGB/Bayer + single focus + integrating sphere approach. I wanted to explore a little more of the possibility space than we usually see in the homemade 8mm machines to see if I couldn’t dig up that 10%.
That said, I am trying to mentally prepare for the event that we find all my extra effort only gives 0.5 or 1% of whatever this nebulous “benefit” ends up being. In that case the effort will have still been useful, if only as a cautionary tale for others to avoid in the future! 
At the very least, I just want to transform some of my conjecturing into real data points. And… you know, maybe scan my family’s 8mm films while I’m at it.
That’s another interesting position that is counter to my intuition, especially given your own demonstration of the same effect when using an integrating sphere. (Granted, my intuition is severely underdeveloped in the area of optics, to the point of being wrong most of the time. So these contradictions are useful for helping me sort out my own mistakes in understanding.)
Is your claim that that the magnitude of the aberration will just be lower with an integrating sphere? Isn’t the image focal plane determined solely by the imaging lens (between the sensor and subject) and the light wavelength? Would the angle of incidence of the illumination behind the subject have anything to do with it?
FWIW, last night I ordered some barium sulphate and those small cake pans that @PM490 has mentioned a few times. I want to test two things:
- The usual case: integrating sphere exit pupil placed as close to the subject as possible, just to compare/contrast my other results.
- Integrating sphere used as the input to the Köhler setup.
The reason for the latter is that despite trying to pack these LEDs in as tightly as possible on this PCB (in the top post), even with the “perfectly out of focus” lens setup, there are still (large, smooth, but) uneven hotspots in the image unless I put a diffuser or two at the beginning of the light path. Starting with an ideally even field and then using the lenses/apertures just to adjust the contrast seems like an interesting experiment.