m42 lenses on K3 - double the SLR primes or not?

[idrawthings]

Conventional wisdom on this board seems to hold that if you use, say, a 50mm m42 prime lens on the K3, you should expect the results on your film to be roughly that of a 100mm lens.

I just popped on a 50mm m42 prime onto my k3, looked through the viewfinder and aligned the frame so that my kitchen counter was flush with the bottom of the frame, and a point on the ceiling aligned to the top of the frame. Remaining in the same spot, I remounted the stock zoom (17-69mm), and zoomed until the viewfinder frame lined up with those same points. Looked at the zoom ring (or knob or whatever) and it was at about 50mm.

The conventional wisdom always made sense to me - what am I missing? Any insight would be great, especially before I dive into anymore lens purchases.

[Patrick]

I believe it should be more than double the magnification. I purchased a 400mm m42 screw mount lens for my K3. Mounting the lens and viewing my kitchen through it, I paid close attention to framing and coverage. I then mounted a 600mm mirror lens with a 2x teleconverter (which makes effectively a 1200mm lens) to my Canon AE1 and viewed the same scene and compared. The field of view provided by both lenses was pretty much the same - not exactly but roughly.

[paulcotto]

The film frame for 35mm movie film runs vertically causing the exposed area to be about half as big as a 35mm still camera. That might account for the phenomenon you describe.

Regards,
Paul Cotto

I believe it should be more than double the magnification. I purchased a 400mm m42 screw mount lens for my K3. Mounting the lens and viewing my kitchen through it, I paid close attention to framing and coverage. I then mounted a 600mm mirror lens with a 2x teleconverter (which makes effectively a 1200mm lens) to my Canon AE1 and viewed the same scene and compared. The field of view provided by both lenses was pretty much the same - not exactly but roughly.

[lunni]

Conventional wisdom on this board seems to hold that if you use, say, a 50mm m42 prime lens on the K3, you should expect the results on your film to be roughly that of a 100mm lens.

I just popped on a 50mm m42 prime onto my k3, looked through the viewfinder and aligned the frame so that my kitchen counter was flush with the bottom of the frame, and a point on the ceiling aligned to the top of the frame. Remaining in the same spot, I remounted the stock zoom (17-69mm), and zoomed until the viewfinder frame lined up with those same points. Looked at the zoom ring (or knob or whatever) and it was at about 50mm.

Yes. 50mm is 50mm is 50mm!

Focal length doesn't change whatever you do. Field of view is different on 35mm and 16mm camera though. 50mm lens on 16mm camera gives you approximately same coverage as 100mm lens on 35mm camera.

[bakanosaru]

This question comes up regularly (because it is so confusing perhaps?), the answer is this (I think):

the focal length of a lens does not change between formats (8mm, Super 8, 16mm, 35mm, etc) it's angle of view changes.

In this case a m42 50mm will have the same angle of view as the zoom that comes with the K3 when at 50mm. However, the angle of view that it has on the K3 will be roughly equivalent to that of a 100mm lens on a 35mm camera. Just as using a 8mm fisheye designed for 35mm cameras will yield only a standard(ish) field of view on a super 8 camera.

If you search the forum (try using Google) I'm sure you'll find a much better answer.

[Will2]

Focal length is the same because it is inherrent to the lens; coverage is smaller because its almost half the size of film hence it seems like a different focal length.

I think you already understood this, so sorry if I'm stating the obvious.

It seems like its not that important of a distinction but it kinda is because things like lens edge distortions are of course minimized because you're only using the center part of the lens.

On that tangent, with a K3 in super-16, lens distortions will show up more on the right side of the frame because the wider gate isn't centered with the lens. Kinda strange with some lenses, not that noticable on others.

[zaefod]

Focal length is the same because it is inherrent to the lens; coverage is smaller because its almost half the size of film hence it seems like a different focal length.

I think you already understood this, so sorry if I'm stating the obvious.

It seems like its not that important of a distinction but it kinda is because things like lens edge distortions are of course minimized because you're only using the center part of the lens.

On that tangent, with a K3 in super-16, lens distortions will show up more on the right side of the frame because the wider gate isn't centered with the lens. Kinda strange with some lenses, not that noticable on others.

I have found that my my 50mm Takumar covers the super 16 area just fine. Primes seem to work with out vignetting. The stock zoom vignettes after 27mm or so. IN any case, there are not that many wide angle primes to choose from. I have heard mixed things about the Peleng 8mm. I like a lens to be razor sharp like the Takumar or Zeiss Jena. my two cents.


Chris

[Justin Lovell]

strangely enough, I tried my nikon 18mm wide lens (for 35mm still camera) on my bolex and it gave a wider field of view than my 18mm POE (bolex 16mm zoom lens.)