Inspecting film?

[Steve Goldstein]

There have been several comments about Efke PL25 quality problems in the current thread about demand for an ISO 25 film. I wonder, are the kinds of emulsion defects reported something that would be visible on unexposed sheets with an IR viewer? For those folks with a freezerful of the stuff (alas, not me), this might be a simple way to discard the worst sheets before going to the trouble of exposing and developing it.

[Sevo]

A visual check with IR video goggles is rather unlikely to find pinholes smaller than a centimetre. The ones EFKE could not find themselves are two or three magnitudes smaller. And building a IR microscope and going over entire films by hand in millimetre increments would be too tedious. About the only feasible way I can think of would be to hack a flatbed scanner so that it will only do a purely IR channel scan (Digital ICE etc.), remove the visible light source (or cover it with an IR lowpass filter), remove all its LEDs, put the control computer into a separate room, and evaluate the resulting scans with some script that counts/locates pinholes automatically. Probably not worth the cost and effort given the dwindling amount of Efke sheets - but it might be worth while if some other maker takes a turn towards being cheapest at the price of poor QC.

[Steve Goldstein]

Thank you. From the discussion I had the impression that the problems were large enough to be easily visible, but pinholes certainly would not fall into this category.

[Brian C. Miller]

What Efke lacked was an automated process. Film is cut and packed at a very fast pace, and a 1/2-inch defect is easy to miss. Kodak, Fuji, and Ilford have machinery to scan for defects like these, so of course you never see them. I have no personal clue if a 1/2-inch defect would be visible under IR goggles. But for me that's academic, as I used their roll film and infrared sheet film, neither of which can be inspected in that manner.

[Jac@stafford.net]

I am one who had problems with one batch. I also sometimes use IR goggles in the darkroom to cope with handicapped hands. There is no way to visually detect emulsion flaws. That is my experience, anyway.

[gleaf]

Automated sheet scanner. Hmmm.
Convert scanner with a IR range sensor. not to difficult.
Automate a sheet feeder handler. Vacuum cups and air to vacuum venturi, valves etc.
Scan a box at a time. Might be DIY able. Throughput If a master roll
is equal to 500 boxes of 25 ea 4x5.. Keep someone off the streets at night.

[Vlad Soare]

I am one who had problems with one batch. I also sometimes use IR goggles in the darkroom to cope with handicapped hands. There is no way to visually detect emulsion flaws. That is my experience, anyway.

Mine, too. There's no way you can see emulsion flaws with infrared goggles.