Different lenses create different frame spacing. Why?

[Abram]

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Hey everyone,

 

I have a question to ask that I can't seem to figure out on my own. When I'm using my 21mm Super Angulon (regardless of the film camera) the frame spacing is so tight that each frame is nearly touching (though it is consistent from shot to shot). When I use any other lens, say a 35 or 50mm, the spacing is perfectly normal and consistent. What is it about the wide angle that's causing the frame to come out wider than normal? I can't seem to wrap my head around it.

[pgk]

If you are talking about film cameras its probably because of the way the lens projects into the camera. The extreme angle of incidence onto film may mean that its projecting the image in such a way that it effectively 'creeps beyond' the film 'gate' and thus gives a marginally larger image than lenses with a different projection.

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[a.noctilux]

It's simple geometric/optical trics.

 

Light bending power and distance to film is different with optical formulas.

With symetrical lens like the Super-Angulon 21mm, the emerging wave from the lens is near the film.

So the coming light just can "look around corner" with wider field as consequence on film than your other lenses.

 

Something like this (quick sketch, sorry if it's not clear )

 

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Edited March 8, 2018 by a.noctilux

[Pyrogallol]

I have noticed this more in the last few years since I have been printing “Cartier-Bresson “ style showing the whole negative including the rebates outside the negative to get a natural black border. I have a 21mm f4 Super Angulon which produces the widest negatives.

 

I think that it is because the beam of light leaving the back of the lens heading towards the film is traveling at a wider angle, from a starting point closer to the film and the light is passing under the metal framing just in front of the film at an angle that lets it produce a slightly wider picture. The effect is most noticeable with wide angle lenses and a bit smaller with long focal length lenses.

 

I think the same wide angled beam of light means that in digital cameras the individual pixel sensors have to be angled so that those at the edges of the sensor are looking inwards at the light while the ones in the centre are looking straight out so that they are all trying to see the light at 90 degrees to their surface.

 

That is what I think?

[Abram]

Ah ok! This is really helpful guys thank you!