I’m rather new to DSLR scanning but after getting some already impressive first results compared to my “professional” Minolta Dimage Scan Multi 2, and previous Minolta Dimage Scan Dual (both some 10-15 years ago) I’m getting enthusiastic. My recent switch back to film added motivation. Overall, I’ve been reading the very helpful discussions here, and anything else that could be helpful on the web, and am on a steep learning curve. After some playing around with my iPad, and a custom film guide stuck on opalescent glass, I decided to dive in and build a proper rig. It needs to be smart and cheap (…) but very good and convenient. So far, I’ve come to the following conclusions:
- Cheapest good copy stand is an old enlarger
- Cheapest good film holder is either from such an enlarger or gluing some film strips as guides on a glass plate and covering that with something flat with a window the size of the to-be-scanned area.
- Cheapest in-line dust clean solution are two antistatic carbon brushes for cleaning LP records mounted on top of each other through which film is pulled before entering the scan area. Additionally soft silicon “sticky rollers” could be implemented.
All straight forward and simple enough with many good examples already shown on the discussions here.
What I’m currently stuck at is the physics of the light source, and being a physicists myself, I suspect that I could come up with some solutions that make sense (perhaps…). What I’ve learned so far is that in old enlargers, one usually has two options: Using a “condensor/condenser” which, as far as I could distill, collimates the light source, or in normal words, makes the light travel perfectly parallel and fall perpendicular onto the negative. This will give the sharpest scan (or enlargement). Alternatively, as far as I understood, one would use a “diffuser” (frosted or opalescent glass) to create diffused light (light from all directions) falling onto the negative. This will result in a softer enlargement (and thus scan) with less sharp borders/transitions and softened film grain.
I assume that we all want the sharpest scans possible, so my conclusion was that a well collimated light source is best, which would render all LED panels and the like non-optimal. Hence, I’m embarking on route to generate a proper collimated light source.
One option would be to use the light source in an old enlarger together with its condensor. I don’t know how well collimated this light would be, but I assume that folks that built enlargers with condensors for many decades knew what they were doing. Alternatively, one could use any lens, place a point light source at the position where the film would be, put the lens on infinity, and what should come out of the front of the lens should be perfectly a perfectly parallel beam of light. The negative should then be placed on top the the front of this lens in the collimated light, held perfectly flat, and scanned.
Does this all make sense? Do LED and diffused iPad light sources intrinsically yield soft scans, and does a properly collimated light source indeed yield sharper results? Physics says that a collimated light source should indeed be better, but please chime in or tackle whatever I might have misinterpreted.