Light sealing material for old reusable casettes

guangong said:

To repeat, never had this happen in 60 years with Leica IIIA, IIIC, IIIF, various Canon rf cameras, Nikon rf, or Contax 2a.
I just don’t see how sprocket holes can be exposed if film is being held in place and advanced with sprockets. I can see it happening if haste in loading causes sprocket holes not to be engaged. Since sprockets are out of sight with Leica LTM I can see this happening if in a hurry. Knock on wood...hope it never happens to me.

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There are no sprockets at the cassette end. There is nothing to stop the cassette moving up and down if it has freedom to do so. The film is not being held in place by the sprockets: they just pull it through. The attached 1952 book illustration (from Kisselbach's Kleines Leica-Buch, page 20) shows what I am talking about.

Ballinderry-Michael said:

There are no sprockets at the cassette end. There is nothing to stop the cassette moving up and down if it has freedom to do so. The film is not being held in place by the sprockets: they just pull it through. The attached 1952 book illustration (from Kisselbach's Kleines Leica-Buch, page 20) shows what I am talking about.View attachment 350741

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If the sprockets are pulling film through the film gate, wouldn’t the film be aligned properly at

Ballinderry-Michael said:

There are no sprockets at the cassette end. There is nothing to stop the cassette moving up and down if it has freedom to do so. The film is not being held in place by the sprockets: they just pull it through. The attached 1952 book illustration (from Kisselbach's Kleines Leica-Buch, page 20) shows what I am talking about.View attachment 350741

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If the sprockets are pulling film through the film gate, wouldn’t the film be properly aligned at the film gate? Perhaps not! I just find it interesting that nobody that I know among a host of Leica users ever mentioned this as a problem, although during 60 years using Leicas I have managed to create other unique screwups. I never had to insert anything to raise any cassette, no matter the film brand.
I am not doubting that an image can appear at the sprocket holes, but I still believe it’s due to human error.

According to Mark Train, even God can screw up. After making man, he tried to rectify the situation by making chimpanzees.

guangong said:

To repeat, never had this happen in 60 years with Leica IIIA, IIIC, IIIF, various Canon rf cameras, Nikon rf, or Contax 2a.

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It's not an issue with Canon, Nikon, or Contax. It is, however a very well known issue with Leica thread-mount cameras. Your experience is super but it doesn't trump the experience of virtually everyone.

guangong said:

I still believe it’s due to human error.

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It is due to the difference between the height of a Leitz cassette and a regular commercial cassette. Using the Leitz cassettes positions the image centred.

You should look at your negatives and see where the image is. Chances are, it's closer to one row of sprocket holes than the other.

Anyway - arguing about this is nonsensical. It's very well-established that this happens.

guangong said:

I have been using standard cassettes in Leica M cameras since mid 1960s, first time I ever heard about the need for a spring.

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Ballinderry-Michael said:

No. It arises simply because the earlier Leica cameras have a "higher" space to accommodate the cassettes. There is no problem with Leitz cassettes: they are "higher" than what you call regular cassettes. My IIIf has a baseplate with a flange that keeps the film up in place inside it: my II does not and needs a shim when I put regular cassettes into it. Nothing to do with loading.

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I spoke of this issue, because mine was a IIIC and, the spring kept the purchased cassette film where it was needed.