joachim
Convicted Ektachome user
Hi,
I only noticed this yesterday. When using the 21mm Biogon (for Contax G), the images on the film are larger (about 0.5mm in either direction) then when using either of the longer lenses. I noticed it, because the spacing between the frames was very small when using the Biogon. Checking against the perforation, there is definitely not a frame spacing issue with my camera.
The reason must be that there is quite a distance (1 or 2 mm) between the gate in the camera and the film. Due to the light rays hitting the frame corners at a steep angle, the rays get further out with the Biogon than do for the longer lenses.
I think it is all quite amusing. Anyone else noticed that before? I have never see this discussed anywhere.
I only noticed this yesterday. When using the 21mm Biogon (for Contax G), the images on the film are larger (about 0.5mm in either direction) then when using either of the longer lenses. I noticed it, because the spacing between the frames was very small when using the Biogon. Checking against the perforation, there is definitely not a frame spacing issue with my camera.
The reason must be that there is quite a distance (1 or 2 mm) between the gate in the camera and the film. Due to the light rays hitting the frame corners at a steep angle, the rays get further out with the Biogon than do for the longer lenses.
I think it is all quite amusing. Anyone else noticed that before? I have never see this discussed anywhere.
Justin Viiret
Established
My 25/2.8 ZM Biogon does exactly the same thing on my M3. 
sepiareverb
genius and moron
And you'll notice the 90 gives slightly smaller images. Negative size will vary with all lenses for exactly the reason you surmise.
ernesto
Well-known
That is because the light rays that reaches the film, comes at diferent angles, so the distance of the metal frame window to the film plane, in the camera, is projecting a diferent shadow, resulting in a diferent frame size.
Note that the metal frame in the camera is NOT touching the film, to prevent any scratch or damage. This tiny space is the responsible for the shadow shift.
If the FOV of a certain lens is 90 degrees, this means that the rays touching the image borders would come at 45 degrees aproximately. In such a case assuming that the distance between the metal frame and film plane would be 0.25mm this will result in a 0.5mm bigger image on film.
Ernesto
Note that the metal frame in the camera is NOT touching the film, to prevent any scratch or damage. This tiny space is the responsible for the shadow shift.
If the FOV of a certain lens is 90 degrees, this means that the rays touching the image borders would come at 45 degrees aproximately. In such a case assuming that the distance between the metal frame and film plane would be 0.25mm this will result in a 0.5mm bigger image on film.
Ernesto
Roger Hicks
Veteran
Yup. Basic geometry. Addressed in A History of the 35mm Still Camera, Focal Press, 1984.
Cheers,
R.
Cheers,
R.
Keith
The best camera is one that still works!
I've always been intrigued by the way the light bends or bleeds into the negative outside of the frame if you get a strong highlight right on the edge of the frame!
ernesto
Well-known
ernesto
Well-known
That is a diferent problem.
When the exposure is right, only direct light affects film.
But if an overexposure happens, the film will catch not only direct light but also indirect light reflecting and refracting on the film itself and against everything arround the camera frame.
Normally direct light is several times stronger compared to any possible indirect light inside the camera, so it is invisible in a photograph.
But, sometimes if you have decided to expose for the shadows, and a strong light source appears near the picture borders, it can do the trick.
This strong light will be "overexposed" and film will have the chance to catch indirect light arround the overexposed area.
Ernesto
Roger Hicks
Veteran
Tom A
RFF Sponsor
This is common with wides and ultrawides. My old Biogon 21f4.5 for Contax does it and my Super Angulon 21f3.4 in M mount does it in *****s. The "strip" between negs gets minimal (a mm or so) - makes it difficult to cut negs for filing!
It also scrambles attempt to get even black lines from "full frame/black line " printing in the enlarger.
It also scrambles attempt to get even black lines from "full frame/black line " printing in the enlarger.
projectbluebird
Film Abuser
I've never noticed the larger frame size, but I have noticed another interesting "quirk" of my VC 15/4.5 superwide. Being a rectilinear lens, it projects a rectangular image. The screw-mount adapter I use to mount it on my M3 must be slightly out of spec, because the image is ever so slightly tilted out of parallel with the film edges. I only noticed this when I was trying to scan full frame/black line, like Tom is talking about.
(When I printed those same negs in the darkroom I must have just turned the easel!)
(When I printed those same negs in the darkroom I must have just turned the easel!)
Erik van Straten
Veteran
quote: "Being a rectilinear lens, it projects a rectangular image."
Every lens projects a circular image, the 15mm Heliar also.
Erik.
Every lens projects a circular image, the 15mm Heliar also.
Erik.
joachim
Convicted Ektachome user
If I understand correctly what you are writing, then this is a camera issue. The part of the gate which limits the image is not parallel with the film. The lens can not do this.
projectbluebird
Film Abuser
And yet it does. No other lens I own does this.
The reason I make this seemingly outrageous claim, is that with the M-mount adapter my Super-wide heliar doesn't mount entirely level with the VF on my M3. Really only a very slight difference. The tilt on the negatives taken with this lens, and only this lens, is also very slight. I may be wrong, and correlation doesn't always imply causation, but that's the logic as I see it.
There's nothing wrong with the film gate on my M3, and as far as I can tell the film gate, film channels and the rest of the shutter frame are of a single piece. If anyone can come up with another explanation, I'd love to hear it.
Tom A
RFF Sponsor
Is this a consistent problem with the CV 15 or just one roll? If it is just a single roll or a couple - it could be something as simple as the filmcassette not being pushed all the way "home" or the film not tracking "true" through the camera.
The frame on the film is created by the filmgate in the camera and should not "vary" except for the occasional "creeping" of light under the edges of it when using some wide-angle lenses. The original Hologon 15f8 would have images almost butt up against each other as does the 12f5.6 Ultra Heliar and the f3.4 Super Angulaon 21mm. The Heliar 15 does it too, but to a lesser degree.
The frame on the film is created by the filmgate in the camera and should not "vary" except for the occasional "creeping" of light under the edges of it when using some wide-angle lenses. The original Hologon 15f8 would have images almost butt up against each other as does the 12f5.6 Ultra Heliar and the f3.4 Super Angulaon 21mm. The Heliar 15 does it too, but to a lesser degree.
projectbluebird
Film Abuser
Every roll I've shot with the CV 15, and scanned, has had this problem. That's actually how I discovered it in the first place, because every frame was not parallel to the scanner tray! I don't have any recent negatives with this lens at hand, or I'd check them too.
You may be right about the film tracking Tom, the commercial rolls are slightly worse than the home loads, and I only use IXMOO cassettes for bulk film. But weren't the IXMOO's developed specifically for the M3? I know the older cassettes won't work.