Re: [Leica] Negative size

[Dennis Painter <dwp@deltanet.com>]

George Huczek wrote:
> 
> Every once in a while I come across something that I read that takes me by
> surprise.  A case in point occurred yesterday.  I was reading David
> Vestal's "The Craft of Photography", one of Mike Johnson's recommended top
> 10 which is worth reading.  The edition I have is quite old (1975), written
> at a time when David was still using an M2, a Miranda sensorex, and a MF
> Rolleicord.
>    He is writing about enlarging equipment, discussing the way to file down
> a negative carrier to print full frame.  He says,
> 
> "A glassless carrier can be carefully filed down so the opening is slightly
> larger than your largest negatives (the ones made with wide angle lenses)."
>  p 123
> 
>    I was always under the impression that negatives in 35mm were all the
> same size, based on the size of the film gate in the camera.  I have never
> noticed that negatives made with wide angle lenses are slightly larger than
> those made with other lenses.  Can anyone verify that negatives made with
> wide angle lenses are, in fact, slightly larger?  It just doesn't sound
> right to me, so I thought I would ask to see if anyone knows whether or not
> this is true.
> 
> -GH

George,

It depends on the WA lens. But the neg can be larger than 24x36, mostly
in the longer dimension since that is where the greatest relief is in
the film mask in the camera.

With the 21mm f3.4 SA the neg gets to about 24x38mm or thereabouts.

If you look at the relationship of the rear element and the film plane
you will see that on the 21 SA the center of the rear element is about
1/4 inch from the film plan.  Thus the light rays that go to the edge of
the film mask are coming at a very shallow angle and can 'peek' under
the edge of the mask extending the coverage beyond the nominal 24x36.

Dennis