OT: wide angle lenses and crop factors

[zuikologist]

This is connected to RF photography (sort of):

I am thinking of using some old M42 mount and LTM lenses on a Canon DSLR with appropriate adaptors, just for variety. I know the crop factor for the APS sized sensors is generally about 1.4 - 1.6, but apparently works differently for ultra-wide and wide lenses (15-24mm). Any information would be welcome.

Apologies if this has been covered elsewhere.

 

[phototone]

I have not heard that the crop factor "varies" with focal length, and I fail to see how it would, since the "sensor" stays the same size, and lens focal length is fixed.

 

[Nikon Bob]

I have never heard the the crop factor is different when using wide angle lenses. I would just determine what the crop factor is for the sensor size in use and go with that.

Bob

 

[Doug]

LTM lenses on the Canon dSLR will not focus to infinity... I hear a lot of people talking about adapting older non-Canon prime lenses, but it seems to me the resulting manual diaphragm operation would be irritatingly inconvenient. I've used manual-diaphragm lenses and even pre-set lenses are so awkward and error-prone I wouldn't even consider it. Except maybe for macro use on tripod. But obviously some gladly put up with that!

 

[phototone]

It is my understanding that Leica SLR type lenses can be used at infinity with an adaptor on Canon mount SLR cameras. Still the crop factor would be whatever the "sensor" size is, from Full Frame on the 1Ds Mk II, the new 5D, to what 1.5 on a Digital Rebel?

 

[zuikologist]

Thanks you all for the responses.

I had read about the crop factor point in an issue of Amateur Photographer this year - I guess they were wrong. I may try to find the issue again. Perhaps for a DSLR it is not so much of an issue anyway - what you see is what you get (mostly).

I think Bill Mattock mentioned in an older thread that he used together an LTM/M42 adaptor and M42/PK adaptor on his Pentax DSLR and was happy with it (correct me if I'm wrong Bill!). I was thiking of trying the same combo.