Stephanie Brim said:
There should be less grain. Much less. I've run this batch of Tri-X through Rodinal before ( a couple rolls, actually) with less grain.
Welcome to the unpleasant world of grain aliasing (
this link to the Photoscientia website is still the most authoritative source.)
It's basically a statistical phenomenon that occurs when the (regular) spacing of the scanner pixels approaches being an even multiple of the (random) spacing of the film's grain structure. The interaction of the regular and irregular patterns causes the irregular pattern to be magnified, somewhat like the "moiré" effect you see if you lay one piece of sheer silk fabric across another piece.
The result is that a print of your scanned image will appear much grainier than a wet print of the same negative. (Printing paper is so fine-grained that for all practical purposes it produces a continuous-tone image that doesn't interact with the film's grain structure.)
The Web is full of incomplete explanations and partial "solutions" that don't really work. Anything you can do that reduces the excess graininess will also reduce the sharp appearance of the grain structure (which presumably is what you wanted, since you were using Rodinal!) There are some software solutions that may help in some cases -- I've had some success with the Noise Ninja plug-in -- but you always lose some sharpness and/or texture.
The only simple answers are to use a scanner with a pitch finer than the grain structure (some people claim the discontinued Minolta 5400 II can achieve this) or to shoot on chromogenic b&w films instead of traditional silver-based films. The chromogenic-film image is formed of soft-edged dye clouds instead of hard-edged halide grains, so it doesn't trigger the grain-aliasing response.
Having said all that, I've had some success with the following slow and irritatingly complex procedure for scanning my T-Max P3200 negatives:
-- Load the film in the scanner and set it to scan at its highest resolution (4000 ppi in the case of my sharp-but-slow Canon FS4000 scanner.)
-- Using the scanner's manual exposure controls, make a scan that's light enough to capture all the image's shadow detail. The highlights will be blown out; we'll fix that in the next step.
-- Scan again, this time using a setting that captures the highlight detail, even if this makes the midtones and shadows too dark.
-- If the negative has a really wide density range, you may need a third scan just for the midtones, although I've only encountered this situation once or twice.
-- Now, assemble all the scans as layers in one Photoshop document. You may find a different procedure makes more sense to you, but I like to put the light image on the bottom and the dark image on top, and set the dark image's transfer mode to Multiply. Then I adjust the opacity of the dark image until I have a fully-toned composite image. If the image needs "dodging" or "burning", I create layer masks to apply local corrections, duplicating the light or dark layer if necessary to add more tone in a specific area. (I know you're a Photoshop gurette, so I won't go into detail on how to do all this stuff; you also can get even fancier with problem negatives by adding adjustment layers and such for super-precise local control.)
-- Finally, to fix grain aliasing: Often the composite image will have less apparent grain without any tweaking, simply because the scanner's mechanism won't index both scans in
exactly the same position; the slight difference causes a supersampling effect that breaks up the aliasing. If you want to try suppressing the grain still further, select one of the layers and use the arrow keys to move it left, right or diagonally in one-pixel increments. Often a one-pixel move in the right direction will suppress the aliasing while maintaining a natural appearance of the grain.
Good luck and have fun!
