DIRTY HARRY wrote:
My question about photographing negatives on a light box over using a scanner is .. is there a difference in the quality of the download? Is a 120 size negative at 14 mp - 19 mp as good as as one scanned at it's highest level?
Copying 35mm slides and negatives with macro photography works best for me. But scanning 120 and larger films works best when you need a very large file. The key is that scanners simply work better with less enlargement. (Now, if I had a Hasselblad Flextight X5 scanner ($25,700), I would get much better scans of 35mm with that! But I'm not running a high-end service bureau in the NYC photo district.)
Sub-$2000 Flatbed scanners are not inherently sharp. If you put the negative on the scanner glass, you might get Newton's rings. If you put it in a holder, it's slightly out of focus, requiring extra sharpening in post production.
I am able to retain sharp film grain in my macro photos of 35mm and smaller negatives. If you can see the film grain, the *image* on the film isn't going to get any sharper.
A note about file sizes... At a common lab standard of 240PPI, my 16MP Micro 4/3 un-cropped image will make an excellent 19.2x14.4 inch image. It will make an acceptable 40x30 inch print of most subjects. But if you take a 5x4 and scan it at 2400 dpi (for a 12000x9600 pixel image), that will make a wonderful 50x40 inch print at 240 PPI. It would make an acceptable 100x80 inch print of most subjects.
Take into account the grain structure of 35mm film... Prints much larger than 20x16 are going to be a bit grainy, unless the film was rather slow (ISOs 64 and slower). That said, judicious use of noise reduction while post-processing can eliminate quite a bit of grain without killing detail, when you coordinate noise reduction with sharpening.
A direct answer to your question is that a 120 negative (arbitrarily, 6x4.5 cm format) copied with a macro lens will have less grain than a 35mm negative of the same film emulsion, but I might not see all the available detail. I'm pretty sure a Nikon D850 with a macro lens WOULD gather all the detail, however. It would probably do so with a 4x5.
Now, the Olympus OM-D E-M1 Mark II or Panasonic Lumix G9, with the 80MP high resolution mode, would be a beast. It would grab all the details of 120 film formats up to 6x9, and probably 4x5 as well.