In another thread Bart mentioned the use of a slanted edge target on a flatbed to deliver a suitable base for the sharpening. I would be interested in an optimal deconvolation sharpening route for an Epson V700 while still keeping grain/noise at bay. Noise too as I use that scanner also for reflective scans.
Allow me to make a few remarks/observations before answering. The determination of scanner resolution is described in an ISO norm, and it uses a "slanted edge" target to determine the resolution (SRF or MTF) in 2 directions (the fast scan direction, and the slow scan direction):
Photography -- Spatial resolution measurements of electronic scanners for photographic imagesPart 1: Scanners for reflective media
andPart 2: Film scanners
In both cases slanted edge targets are used, but obviously on different media/substrates. These targets are offered by several suppliers, and given the low volumes and strict tolerances they are not really cheap.
I have made my own slanted edge target for filmscanners, as a DIY project, from a slide mount holding a straight razor blade and positioned at an approx. 5.7 degrees slant. This worked slightly better than using folded thin alumin(i)um foil, despite the bevelled edge of the razor blade. I used black tape to cover the holes in the blade and most of the surface of the blade to reduce internal reflections and veiling glare.
This allowed me to determine the resolution capabilities or rather the Spatial Frequency Response (=MTF) of a dedicated film scanner (which allows focusing), in my case by using the Imatest software that follows that ISO method of determination. It also allowed me to quit scanning 35mm film when the Canon EOS-1Ds Mark II arrived (16MP on that camera effectively matched low ISO color film resolution). I haven't shot 35mm film since.
There is however an important factor we might overlook. When we scan film, we are in fact convolving the ideal image data with the system Point Spread Function (PSF) of both camera (lens and film) and
the scanner (assuming perfect focus). That combined system PSF is what we really want to use for deconvolution sharpening. The scanner PSF alone will help to restore whatever blur the scan process introduced, but it produces a sub-optimal restoration when film is involved. It would suffice for refection scans though, it could even compensate somewhat for the mismatched focus at the glass platen surface used for reflection scans.
Therefore, for the construction of a (de)convolution kernel, one can take a photographic recording of a printed copy of a slanted edge target, on low ISO color film. One can use a good lens at the optimal aperture as a best case PSF scenario. Even other areas of the same frame, like the corners, will benefit. For a better sharpening one can blend between a corner and the center PSF deconvolution. One can repeat that for different apertures and lenses. However, that will produce a sizeable database of PSFs to cover the various possibilities, and still not cover unknown sources.
Luckily when a number of blur sources are combined, as is often the case with natural phenomena, the combined PSFs of several sources will resemble a Gaussian PSF shape. This means that we can approximate the combined system PSF with a relatively simple model, which even allows to empirically determine the best approach for unknown sources. It won't be optimal from a quality point of view, but that would require a lot of work. Perhaps close is good enough in >90% of the cases?
So my suggestion for filmscans is to try the empirical path, e.g. with "Rawshooter" which also handles TIFFs as input (although I don't know how well it behaves with very large scans), or with Focusmagic (which also has a film setting to cope with graininess), or with Topazlabs InFocus (perhaps after a mild prior denoise step).
For reflection scans, and taking the potentially suboptimal focus at the surface of the glass platen into account, One could use a suitable slanted edge target, and build a PSF from it. I have made a target out of thin selfadhesive Black and White PVC foil. That will allow to have a very sharp edge when one uses a sharp knife to cut it. Just stick the white foil on top of the black foil which will hopefully reduce the risk of white clipping in the scan, or add a thin gelatin ND filter between the target and the platen if the exposure cannot be influenced.
Unfortunately there are only few software solutions that take a custom PSF as input, so perhaps an empirical approach can be used here as well. Topazlabs InFocus allows to generate and automatically use an estimated deconvolution by letting it analyse an image/scan with adequate edge contrast detail. That should work pretty well for reflection scans, because there is no depth of field issue when scanning most flat originals (although scans of photos can be a challenge depending on the scene). Unfortunately, the contrasty edges need to be part of the same scene (or added in the scan file) because I think InFocus doesn't allow to store the estimated solution, but it could save as a preset a normal deconvolution with optimal settings to optimize a PSF or a more simple detailed piece of artwork.
As for sharpening noise, I don't think that deconvolution necessarily sharpens the multi-pixel graininess/dye couds, although it might 'enhance' some of the finest dye clouds. It just depends on what the blur radius is that helps the image detail, and that isn't necessarily the same radius that some of the graininess has.
Sorry for the long answer. Been there done that, so much to explain and take into account.