Variation in density of edge markings - FP4

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I've just developed 4 rolls of FP4, all taken from the same pack of 10. The films were developed in pairs in Jobo 1500 tanks/reels. I'm bewildered to find that in each case, one film shows strong edge markings and the other shows very weak markings. We're talking big differences. The developer was Perceptol 1 + 3. Neg density is inconclusive as I was running tests. Markings are consistent on each side of the films. Markings are consistent along each film - implies there is no inner/outer difference. Films all came from 1 pk of 10 but I discarded packaging so can't check batches.

Any suggestions?

-- Herbert Gibson (herb@nireland.com), April 04, 2001

Answers

Ilford prints a four-digit code on the edge of its emulsions, which probably bears some relation to batch numbers---any difference in those? I've found variants of that number on rolls taken from the same 50-roll pack.

-- Chuck Albertson (chucko@siteconnect.com), April 04, 2001.

I've used 35mm FP4+ in ID-11 for a couple of years now as my standard film and have experienced exactly the same thing. There seem to be two versions of this film, one with lower and one with higher density.

With HP5+ and PanF+ I haven't experienced similar variations.

/omar

-- Omar Ozenir (omar.ozenir@turkcell.com.tr), April 05, 2001.


This is armchair theorizing- I have no inside knowledge, your mileage may vary, and all the usual disclaimers apply. If you were making film, you'd want the edge printing legible. You'd also want to expose the film to the minimum of light to avoid any risk of fogging via light piping or stray light. You wouldn't waste money regulating the light source, or in maintaining consistancy (bulbs?). If you had several machines doing this (likely) you wouldn't worry about minor or even major differences between them- why bother? Production machinery isn't always built at the same time and may not even be of the same optical design. Or run at the same speed. Thus, I suspect judging *anything* by marking density is a complete waste of time. Besides, the marks are too small to measure easily. I do something I think is better, but is still frought with error sources. I make a quick density measurement of the exposed leader of each roll. This should be somewhere near Dmax and gives me at least some confidence that my processing is consistant. Not great, but better than looking at edge markings. You can even do it without a densitometer by comparison with a step tablet.

-- Conrad Hoffman (choffman@rpa.net), April 05, 2001.

black marks on the edges? maybe a low light filtration.

-- Celcio (non@non.non), April 07, 2001.

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