Folds on film & unusual bright-dark stripes

[photonaro]

Hello everybody,

I've been practicing analog photography in the darkroom for about 30 years now and have encountered a phenomenon for the first time - twice within the the last three months - which I cannot explain nor find explanations for online.

It happened to two different students of mine, different films (Rollei RPX400 & Ilford HP5+), different developers (Rodinal & x-tol), different cameras.
Maybe you've got an idea what is happening here.


As they were loading the films on to the spools, they felt a fold on the film toward the end, going evenly all the way from side to side. This was soon to be followed by another fold (see images - first fold at the end of frame 27a, second fold - inverted compared to the first - between 31a & 32a).


This seems to have caused an issue during development: from the point of the first fold onwards there were perforation stripes - though not the common dark or bright - both dark & bright (see images). Up to the point of the first fold the film developed fine.


The images in the photos were intentionally over or underdeveloped as part of an exercise, and they look correctly developed throughout the entire film.
(The contents of the images are blackened as this film belongs to my student).


Have you ever seen something like this or would you have an idea what the cause of it could be?

Any ideas are well appreciated! Thanks

 

[MattKing]

Welcome to Photrio.
At some point in the procedure - either in cassette, in camera or in development reel loading - something has caused the film toget crumpled together.
Are the film cassettes factory loads or bulk loaded from a large roll?

 

[John Salim]

I've seen this many times.
It happens when after a film has been rewound, you try to rewind the film the opposite way round in the cassette causing sharp bends - which in turn mark up the film in those vertical bands.

John S

 

[photonaro]

Ohhh yes, that makes a lot of sense, John - thanks!

Would you have an idea why it causes those marks during development?

@MattKing: The films were factory loaded

Thanks a lot!

 

[Sirius Glass]

/

Welcome to APUG Photrio!!​

 

[AgX]

I've seen this many times.
It happens when after a film has been rewound, you try to rewind the film the opposite way round in the cassette causing sharp bends - which in turn mark up the film in those vertical bands.

Either:

-) as you say, winding the film back by twisting the crank the wrong way.

-) selfspooling the film the wrong direction onto the spool.

In both cases the film is pulled over the inner edge of the mouth of the cassette

 

[AgX]

Would you have an idea why it causes those marks during development?

At pulling the film over a sharp edge it will be bent most extreme each time the longer edge of a perforation passes this edge. In this case the bending took place over the emulsion side.
That extreme bending causes mechanical (pressure-)foggig of the film. This again results at processing in dark bands at these locations.

 

[AgX]

At some point in the procedure - either in cassette, in camera or in development reel loading - something has caused the film toget crumpled together.

Crumbling the film would not yield this effect, as at crumbling the film would be bent alternatively in both directions (leporello),

 

[Nicholas Lindan]

As the film is pulled over a sharp edge it will preferentially buckle/fold at the edges of the perforation holes, the stress of the folding causes the emulsion to 'expose'.

 

[MattKing]

FWIW, I used "crumpling" (not "crumbling") to create a picture in the OP's mind of a film with a bunch of creases in it. And as people have posted, it is the creases that are the problem.

 

[AgX]

FWIW, I used "crumpling" (not "crumbling") to create a picture in the OP's mind of a film with a bunch of creases in it. And as people have posted, it is the creases that are the problem.

But your picture is misleading. As indicated it is not the crease as such that yields this effect, but a crease towards the emulsion side.

 

[foc]

Look at the negative strip in the first image posted by the OP, showing what appears to be stress marks (see below)

The film has a kink/fold from what appears to have been rewound the wrong way into the cassette.
On the left of the kink, the edge markings and sprocket holes show no stress marks.
On the right of the kink/fold the stress marks show.
I have only ever seen stress marks where the film was rewound the wrong way into standard commercial film cassettes.

 

[photonaro]

Thanks a lot for all your answers, it's helped very much, I appreciate it!

Thinking back I'm pretty sure the film was self-spooled in the wrong direction once it was already inside the cassette. That would explain the folds, but there would then be no sharp edge to create the stress marks. Or am I forgetting something?

 

[AgX]

A correctly self-spooled film goes out of its tangential movement straight further into the mouth of the cassette.

Incorrectly spooled it makes after the tangential movement a >90° outward bend at the inner edge of the mouth.

 

[250swb]

I don't think the film was sharply creased during the rewind into the cassette. Instead think about it this way, the rewind button has been pressed so the gears of the film advance mechanism are disengaged, at some point during rewind the direction of winding has been changed pushing just a bit of the film back into the take-up chamber by the natural spring of the film. This loosely folds over into an 'S' shape and the sprocket holes in the fold re engage with the teeth of the film winding mechanism, so now the film is double layered and locked in place by the teeth. As the proper re-wind direction is once again commenced the fold together with the film already engaged on the teeth are pulled back underneath the pressure plate and causing the two sharp creases.



.

 

[photonaro]

I've just tried out with an old practice film both things:

1) to rewind it and change directions inside the camera with the back open, holding the cassette down as if a closed back were doing it.

Incorrectly spooled it makes after the tangential movement a >90° outward bend at the inner edge of the mouth.

The film resulted in very slight, gentle folds and a bumpy texture in the area that was rewinded the wrong way. The folds in my student's film were much more significant, but this may be the right direction of what is happening?


2) to rewind it and change directions inside the camera with the back closed, opening to check the film tension at every step.

I don't think the film was sharply creased during the rewind into the cassette. Instead think about it this way, the rewind button has been pressed so the gears of the film advance mechanism are disengaged, at some point during rewind the direction of winding has been changed pushing just a bit of the film back into the take-up chamber by the natural spring of the film. This loosely folds over into an 'S' shape and the sprocket holes in the fold re engage with the teeth of the film winding mechanism, so now the film is double layered and locked in place by the teeth. As the proper re-wind direction is once again commenced the fold together with the film already engaged on the teeth are pulled back underneath the pressure plate and causing the two sharp creases.

Thanks a lot for the clear illustration. This sounds like a possible idea, but when I tried changing the rewinding direction and then opened the back to see how it looked - the film didn't seem to return even a bit in the direction of the take-up chamber, in any case not enough to allow for another perforation hole to hook up on to the teeth. Instead there was a bit more resistance while spooling in the opposite direction and then it just continued pulling the film into the cassette.


3) to selfspool it by hand and change directions while doing that.
Surprisingly this seemed for some reason not to have much of a visible or tangible impact on the film. I did feel strong resistance when changing directions up to the point that the film tore at the attachment to the spool. But no folds, and just a few, barely tangible bumps only on the last couple of frames.

I'm grateful to all of you who contributed ideas and am remaining curious and open to hearing any additional thoughts

 

[AgX]

I've just tried out with an old practice film both things:

1) to rewind it and change directions inside the camera with the back open, holding the cassette down as if a closed back were doing it.

The film resulted in very slight, gentle folds and a bumpy texture in the area that was rewinded the wrong way. The folds in my student's film were much more significant, but this may be the right direction of what is happening?

As you were quoting me:
I had it not about rewinding, but normally transporting film between exposures. However out of a selfloaded cassetted where the film was mounted wrongly onto the spool and thus spooled, and later transported, the wrong way.
At rewinding such film one only repeats the same sharp inwards bending, what unlikely makes it worse as it already has become.

 

[Sirius Glass]

... This sounds like a possible idea, but when I tried changing the rewinding direction and then opened the back to see how it looked - the film didn't seem to return even a bit in the direction of the take-up chamber, in any case not enough to allow for another perforation hole to hook up on to the teeth. Instead there was a bit more resistance while spooling in the opposite direction and then it just continued pulling the film into the cassette.

.

It may depend on the camera that you are using.

 

[photonaro]

It may depend on the camera that you are using.

That's true. I tried it out with the same camera that my student used, so I suppose I can rule it out for my case. But a good thing to keep in mind in case it appears again in the future with another camera.

As you were quoting me:
I had it not about rewinding, but normally transporting film between exposures. However out of a selfloaded cassetted where the film was mounted wrongly onto the spool and thus spooled, and later transported, the wrong way.
At rewinding such film one only repeats the same sharp inwards bending, what unlikely makes it worse as it already has become.

Oh, I see now better what you meant. In my case it was a commercial cassette.


Over the next few months I'll try a few experiments with exposed film in order to also see the full effect with the stress marks in an intentional and controlled environment and will update my findings here.
Thanks a lot again to you all!

 

[AgX]

At rewinding such film one only repeats the same sharp inwards bending, what unlikely makes it worse as it already has become.

I only know few publications on pressure marks. But one may argue that pressure induced fogging is cumulative, or rather its cause, and thus repeating a certain movement of film may worsen the artefact.

 

[photonaro]

I only know few publications on pressure marks. But one may argue that pressure induced fogging is cumulative, or rather its cause, and thus repeating a certain movement of film may worsen the artefact.

In rewinding the film, the movement is repeated though over a certain length of the film and not on any one given spot. Or have I misunderstood your words?

 

[AgX]

Yes and No...

The film at its virgin width has more strength than at those locations where a hole is. More precisely, where the edges of a hole are. Yielding such stripes artefact.

I admit that thing with the edges of the hole is hard to explain... but I would do so with transport dynamics.

 

[250swb]

I've taught photography and one thing is sure, students will always find brand new ways to cock things up.

 

[photonaro]

Yes and No...

The film at its virgin width has more strength than at those locations where a hole is. More precisely, where the edges of a hole are. Yielding such stripes artefact.

I admit that thing with the edges of the hole is hard to explain... but I would do so with transport dynamics.

I'm not sure I understand what you mean... I don't know whether it lies on language or on the fact that words are sometimes a far from optimal way to describe things... You're welcome to try to describe it in German, if that's allowed here I could then respond in English to make it clear to others.

I've taught photography and one thing is sure, students will always find brand new ways to cock things up.

That's part of what keeps it interesting, isn't it? :-D

 

[AgX]

I would word it the same in German. But you can ask me by PM, to make clear to me what you do not understand.