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Etch Resist as Solder Mask

60x, 60x, 200x photos of Riston film used as solder mask. Now sure how well it will hold up to soldering, though. The first image is a 60 mil pad, the second is a pair of 0603 parts, the third is a BGA pad with 5 mil traces.

6/6.5 Photofilm results

After etch, close-ups (200x). Note the expected undercutting, which resulted in traces just the right size. I "bloat" my films by 1.25 mil per edge.
These traces are all 6 mil on 12.5 mil centers, or about 6/6 rules (technically, 6.25/6.25 rules). Left to right: 200x front-lit, 60x front-lit, 60x back-lit.
Close-up of an 0.5mm TQFP footprint and a via.

Toner Transfer Results

5/5 rules, with traces shrunk 0.83 mil (half a pixel) per edge (i.e. 3.33/6.67 rules).
6.67/6.67 rules, no adjustment.

Lab Setup and TT Calibrations

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