MrNothing wrote in post #14146772
never had any experience with a 50 on a FF. a 85 yes though. putting it on a 1.3 though would be right in between a 50 and a 85 which i guess is a comfortable focal length.
If you've never used a 50mm lens on a full frame camera then why do you care about trying to duplicate it?
in terms of wanting a exact 50mm - eh. it's somewhat of a factor but not compared to wanting a fast lens. i've actually tried putting my lenses at both 35mm (45mm on a 1.3x which is close to 50mm) and 50mm (65mm) and found it a tad awkward at 50mm but better then 35mm. if anything, the extra focal length doesn't hurt then not being close enough to a subject.
If you like the longer focal length better then, again, why are you trying to duplicate 50mm? Why are you wasting your time doing all this crop factor math to duplicate a field of view you have not used instead of picking a lens that gives you the field of view that you want on your camera?
I will suggest that you get the Sigma 50mm f/1.4. It is more reliable than the Canon lens and more important for your needs it is not a 'true' 50mm when focusing at the distances where you are most likely to be using it. When I had one I compared it to several other 50mm lenses and when focused at living room distances the lens is closer to 45mm, maybe even a little wider.