The edges of film

[wintoid]

How is the writing (e.g. frame numbers) on the edges of a film done? Is it pre-exposed, or is emulsion removed when the film is produced?

 

[Roger Hicks]

Pre-exposed, as a thought-experiment will show: fix an unexposed film (we've all done it) and there are no edge markings.

Also, removing emulsion would be a lot more difficult, so why would anyone do it?

Cheers,

R.

 

[wintoid]

Thanks Roger. I always wondered.

As for your thought experiment, presumably you mean develop and fix an unexposed film?

 

[Pablito]

As for your thought experiment, presumably you mean develop and fix an unexposed film?

I don't think so.

 

[Roger Hicks]

Thanks Roger. I always wondered.

As for your thought experiment, presumably you mean develop and fix an unexposed film?

Fixing without development will show that there are NO edge-markings, implying that they are brought out by development, implying that they are pre-exposed onto the film.

Come to think of it, look at the leader. If the emulsion were missing, you'd be able to see that on unexposed, undeveloped film.

Given that films are slit from master rolls, it would be very hard to devise a machine that could remove the emulsion locally without leaving shreds of emulsion everywhere.

Cheers,

R.

 

[wintoid]

Ah yes true, thank you.

But if you fix an undeveloped exposed film, don't you get a clear negative? Getting OT here, because my question is answered, but still interested.

 

[EmilGil]

Yes, you get a clear negative and that's Roger's point. If the edge-markings were done in another way than pre-exposing the film, they would still show up. As they are exposed during manufacturing, they need to be developed before fixing to show up.

If you've never fixed a film before developing it, you haven't been stressed/clumsy enough in the darkroom! =)