MP frame spacing showing some variability

[semi-ambivalent]

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My 3-ish year old MP is beginning  to show some very slight frame spacing variation within a single roll of film. The spacing has always been closer than my M3 but I recall it being very consistent. Not so now. Is this just wearing in or indicative of future issue?

 

Thanks!

s-a

[NB23]

Are you changing lenses during the same roll? I believe a few wide angles will give a slightly bigger frame than a normal lens.

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[semi-ambivalent]

Are you changing lenses during the same roll? I believe a few wide angles will give a slightly bigger frame than a normal lens.

I'll look at the negs but I believe I did. Hadn't occurred to me.

 

thanks,

s-a

[250swb]

Yes a wide angle lens will make a slightly wider negative than a 50mm, and even for a well serviced camera the way you advance the film, two quick half winds rather than one full wind can also cause a small difference in frame spacing.

[FrozenInTime]

If I could have a custom Leica, I would get the inter frame spacing increased to 6mm / 1/4" :

That would make cutting and handling negatives in the darkroom so much easier, especially when printing the entire frame with rebate.

[semi-ambivalent]

If I could have a custom Leica, I would get the inter frame spacing increased to 6mm / 1/4" :

That would make cutting and handling negatives in the darkroom so much easier, especially when printing the entire frame with rebate.

Yes, I used to find it annoying, having grown up with SLRs and Kodachrome. Control framing right to the edges. But I've learned to frame a little looser now and things work fine. Just have to be a little more careful getting the scissors to bite at the right place on a deeply curved stick of Tri-X. Old dog, new trick, blah blah. Printing with a rebate is something else. What do you do if the image is at the end of a stick of (6, say)?

 

s-a

[hoppyman]

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Yes the negative/transparency film frame size can vary significantly with different lenses and of course the nominal view finder frames are intended to approximate a slightly smaller than 24x36 area and only more accurate at a specific distance too.

[Matlock]

Am I missing something here. Surely the frame spacing is dictated by the winding mechanism and the frame size is dictated by the opening in the film gate, the lens has nothing to do with it. The film gate opening is 24x36 whatever the lens.

[TomB_tx]

Because the film gate is a finite distance away from the film, light from wider lenses is diverging when passing the gate, and so spreads out behind it at the film. Thus the lens characteristics do affect the frame size on the film.

[semi-ambivalent]

Because the film gate is a finite distance away from the film, light from wider lenses is diverging when passing the gate, and so spreads out behind it at the film. Thus the lens characteristics do affect the frame size on the film.

Ka-Ching!

 

This occurred to me at some point like, well, duh... You never see it with an SLR because the mirror sets a minimum distance (unless you're using a lens that requires mirror lock-up). Rangefinders are not beholden to that. Good to realize my MP is just going on being gorgeously functional.

 

Thanks!

s-a

[Matlock]

Because the film gate is a finite distance away from the film, light from wider lenses is diverging when passing the gate, and so spreads out behind it at the film. Thus the lens characteristics do affect the frame size on the film.

 

Interesting theory, however on looking through my files, there is absolutely no difference in spacing with my M7. This with 28mm, 35mm, 40mm, 50mm and 90mm lenses on the same roll of film. Even a 135mm lens will provide a wider circle of light than the 24x36 frame.

[Matlock]

Ka-Ching!

 

This occurred to me at some point like, well, duh... You never see it with an SLR because the mirror sets a minimum distance (unless you're using a lens that requires mirror lock-up). Rangefinders are not beholden to that. Good to realize my MP is just going on being gorgeously functional.

 

Thanks!

s-a

 

The mirror on a SLR plays no part in the photo taking process (unless you have a Canon Pellix or high speed F1). It is purely for viewing the shot as is swung out of the light path before the photo is taken.

[NB23]

Interesting theory, however on looking through my files, there is absolutely no difference in spacing with my M7. This with 28mm, 35mm, 40mm, 50mm and 90mm lenses on the same roll of film. Even a 135mm lens will provide a wider circle of light than the 24x36 frame.

This is why I said "a few wide angle lenses" in my answer above. It depends on the angle at which the light hits the film. Something to do with non-telecentric lenses. My super-angulon definitely uses more film area than other lenses, the frames almost touch together.

Edited February 11, 2016 by NB23

[hoppyman]

Interesting theory, however on looking through my files, there is absolutely no difference in spacing with my M7. This with 28mm, 35mm, 40mm, 50mm and 90mm lenses on the same roll of film. Even a 135mm lens will provide a wider circle of light than the 24x36 frame.

The image circle is sufficiently large so that it is not a factor in this. My understanding is that the effect will also vary according to the exact size of the opening revealed by the shutter opening and the distance to the film plane which is not truly flat either. Neither set of dimensions is identical from first M manufactured to current production. 24x36 is nominal only. Still sceptical?   I don't claim any optical expertise at all but I can report what I actually observed. With  my M3 especially this effect was noticeable. Unless you deliberately shot adjacent frames with those focal lengths you may never notice.

 

Possibly related,  commercial printing routinely crops a little by default. Similarly you could check your framing in scanning? If you are darkroom printing, the neg carrier mask is a factor too naturally. 

  

[semi-ambivalent]

The mirror on a SLR plays no part in the photo taking process (unless you have a Canon Pellix or high speed F1). It is purely for viewing the shot as is swung out of the light path before the photo is taken.

I meant the mirror sets a minimum distance it needs for clearance. The lens cannot protrude into this area (unless the mirror is locked up, as is needed by, e.g. the 21mm f/4 Nikkor-O (http://www.destoutz.ch/lens_2.1cm_f4_221921.html)).

 

Regards,

s-a

[Matlock]

The image circle is sufficiently large so that it is not a factor in this. My understanding is that the effect will also vary according to the exact size of the opening revealed by the shutter opening and the distance to the film plane which is not truly flat either. Neither set of dimensions is identical from first M manufactured to current production. 24x36 is nominal only. Still sceptical?   I don't claim any optical expertise at all but I can report what I actually observed. With  my M3 especially this effect was noticeable. Unless you deliberately shot adjacent frames with those focal lengths you may never notice.

 

Possibly related,  commercial printing routinely crops a little by default. Similarly you could check your framing in scanning? If you are darkroom printing, the neg carrier mask is a factor too naturally. 

  

 

I was going on my observations of the actual film strip, not commercial printing (I have been processing my own films for about 50 years). I have only noticed spacing problems with a rather old Praktica which produced some rather interesting effects, sometimes overlapping frames, and my M3 double stroke which I only use with a 50mm lens. I believe that the point that 250swb, re. winding on, made is valid.

[Matlock]

I meant the mirror sets a minimum distance it needs for clearance. The lens cannot protrude into this area (unless the mirror is locked up, as is needed by, e.g. the 21mm f/4 Nikkor-O (http://www.destoutz.ch/lens_2.1cm_f4_221921.html)).

 

Regards,

s-a

 

Sorry, I see what you mean :-)

[250swb]

The further away from the film gate the rear lens element is the less it is going to spread the light under and around the edges of the gate. Further away the light is less spread and more telecentric (going in a perpendicular path towards the film). So an SLR isn't likely to show image creep, except I do remember from a long time ago a deep element wide or fisheye Nikon lens that needed the mirror locked up that made slightly larger images. It's more likely to happen with a rangefinder because the rear element is closer to the film gate, therefore the light covering the edges of the frame is leaving the rear element less perpendicular (at a more acute angle) to the film. But it is those lenses that have deeper rear elements which cause it, so not every type of 21mm design (for example) will do it, only some.

 

Steve

Edited February 12, 2016 by 250swb

[Matlock]

Yes a wide angle lens will make a slightly wider negative than a 50mm, and even for a well serviced camera the way you advance the film, two quick half winds rather than one full wind can also cause a small difference in frame spacing.

 

I still think the winding has the biggest effect Steve. As I said I have only experienced spacing differences with my M3 double stroke which always has a 50mm lens.

One thing that strikes me is that anyone who exclusively shoots digital will wonder what on earth we are all talking about :-)

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[hoppyman]

Am I missing something here. Surely the frame spacing is dictated by the winding mechanism and the frame size is dictated by the opening in the film gate, the lens has nothing to do with it. The film gate opening is 24x36 whatever the lens.

Yes the frame spacing is dictated by the winding mechanism. If there is no slippage or wear in the mechanism then the distance from centre of each frame to the next should be consistent. 

The area/size  of each exposure is unaffected by the image circle as it overlaps the film gate by some margin by design.

I agree with what Tom explained at #9 .You may get some small variation from the nominal 24x36 film gate dimensions due to the film register  (in different camera designs) and different lenses. As I recall using wide angles was where I noticed this.

 

I'm not sure how I noticed this thread as I havent shot film for some years. I think because I measured (with vernier calipers) frames from an M3 some time back.

 

As long as the original poster with his MP has found the discussion helpful it's worthwhile.