How far can film bend?

[Reddkryten]

Hi there.

Just a quick question, does anyone know how far film can be bent before harming
the image?

I was looking at these two images
http://www.flickr.com/photos/okolab/4586428622/
http://www.flickr.com/photos/rachelrayns/5093836952/ which show the film being
bent at a fairly severe angle, will that harm the image?

I was reading up about film kink. I'm planning to wrap the film around a few
nails, I tried this with a piece of scrap film I had, after I had bent and
wrapped the film, I couldn't see any creases. However I'm just wondering, could
the emulsion be damaged in a way that I can't see?

Thanks in advance.
Dean

[carllooper]

Depending on the radius of the bend you'll eventually succeed in putting a kink in the film, damaging a sprocket hole, damaging the emulsion/image, and eventually breaking the film in two (bending it back and forth).

[Reddkryten]

Thank you.

Do you have an approximate idea of how big or small the radius can be? I'm guessing the exact number (a) varies between different film stocks and (b) has probably never been worked out to an exact number. But is there any general radius that could be considered safe?

But yeah, basicially, if the film was stored like in the above pictures for a brief period of time (say an hour or so) would the film be damaged or is the bend gentle enough and time short enough to avoid that.

[carllooper]

The film shown drying in the provided pictures should be fine. You would probably want the emulsion (the shiny side) not in contact with the wires, ie. facing out rather than in. If you look at the inside radius of a film reel you'll see it's quite small. The bends in the pictures look more or less the same as the bends a film would have at the centre of a film reel. Some are shorter but since they are loose they should be fine.

Perhaps the safe radius is the radius a film reel has. If the film could be wound tighter one would imagine reels might have had a smaller radius. That said I believe you could wind a film quite tight and it would still be fine. Some of the bends a film undergoes in some projectors are quite tight.

The real problem is friction more than bending - film rubbing up against a surface - even another strip of film.

[Reddkryten]

Excellent, thank you very much.

[vermaram]

This is very important topic.I was reading up about film kink. I'm planning to wrap the film around a few nails, I tried this with a piece of scrap film I had, after I had bent and wrapped the film, I couldn't see any creases. Thank you :oops:
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