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Old 2nd February 2020, 03:59 PM
Nat Polton Nat Polton is offline
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Default Static. Black spots.

I was looking for an answer to a members problem with black discs on his negatives. I found this. I doubt it was the cause of his problem but I found it interesting nonetheless.



Static can build up on non-metallic surfaces in low humidity cold climates.
Discharge can show itself on the negative as dark marks. Usually branch-like markings. Sometimes as a diffuse spot with a dark centre, (light centre on reversal film) or as a row of bead like markings.

To reduce the risk of static discharges, work in 45% relative humidity where film is handled. If at all possible.

Do not move the film suddenly when stacking sheets or unrolling.

Plastic slides on dark slides should be moved slowly.

Avoid contact with clothing known to be a source of static. Nylon etc. Brings to mind "The Naked Photographer."

If available wipe equipment with an anti static cloth.

Remove film backing papers slowly.

Avoid fast speeds with a motor drive in high humidity conditions.

………………………………………………………………………………..

I have seen static when I pulled a 35mm film out of its cassette in the dark, prior to loading it into a developing tank.
Luckily it did not leave any marks on the film.

Also when I peeled the sticky tape off a 120 roll. That did leave marks but only on the waste end of the roll.



As I mentioned earlier, not the answer to the chaps problem, but some thing to watch out for.


Cheers all.
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Old 2nd February 2020, 07:07 PM
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maltklaus maltklaus is offline
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Polyester-base films also tend to be much more of a dust magnet than traditional acetate-base films
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Old 2nd February 2020, 07:59 PM
John King John King is offline
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Default Static

A long while ago there was a Press Photorapher called Victor Blackman who had a regular article in the Amateur Photographer. He was complaining about the motor rewind with the 'New Fangled' Nikon F2 Photomic.

That was creating static which manifested itself like miniature lightening flashes along the film, as it was rewound into the cassette. They had to revert to hand rewinding to eliminate the problem.

The marks you describe don't sound like any static on film I have seen.
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Old 2nd February 2020, 08:26 PM
Mike O'Pray Mike O'Pray is offline
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I may be particularly lucky in my part of the U.K. but relative humidity I think is quite high over most of the U.K.


Even in a very long hot dry spell I have never seen the relative humidity in my house drop below 60% and it is usually in the mid 60s range. However other parts of the world do get incredibly low humidity by U.K norms

I certainly have never experienced an signs of static that I am aware of

Mike
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Old 3rd February 2020, 05:22 PM
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photomi7ch photomi7ch is offline
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Black spots on negatives are usually coursed by air bubbles. If you have a static problem just earth it.
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Old 3rd February 2020, 08:15 PM
JohnX JohnX is offline
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Yeah, 16mm earth and a brass M8 bolt should do it....lol

err, the black spot thing reminds me of some exposure leak I got through the backing paper of an old roll of FP4
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Old 4th February 2020, 01:43 AM
JulioF JulioF is offline
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Quote:
Avoid fast speeds with a motor drive in high humidity conditions.
This one must have come out reversed. In high humidity conditions there is little chance of static discharge. It happens in low humidity.
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Old 4th February 2020, 07:55 AM
John King John King is offline
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Default black spots

Quote:
Originally Posted by JulioF View Post
This one must have come out reversed. In high humidity conditions there is little chance of static discharge. It happens in low humidity.
Or dampness or film that has been badly stored before you bought it.
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Old 4th May 2021, 09:34 AM
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Roy_H Roy_H is offline
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Default Some pretty (annoying) static for you.

Using Fomapan 100 8x10 film I got these lovely marks yesterday. Never had them before.

My guess is that it happened while separating the paper interleave when loading the film. That paper clings like a limpet to each sheet and on one occasion I have loaded both film and paper accidentally. You only do that once with each sheet now costing over £2.50!

Luckily (or not, given the cost) the subject moved fractionally during the 10 minute exposure so the negative is a reject anyway.

Posted just as a 'heads-up' if you are a Fomapan sheet film user and also as a good example of the wonders of static electricity!
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