I used to use a Palm device for field notes but found going back to digital files to be a pain unless you crossed referenced them in a database. I find my iphone dies at the least opportune time. I have returned to a self printed 3x5 card with film details, lens, exposure notes and zone scale on front, and film processing info on the back. These are numbered and filed with my negatives in my negative storage binders in an empty 4x5 sleeve with images for the month. I no longer bother with 135 format notes except in a notebook if needed.