GH2 Infinity focus problem with canon FD lenses

Essami

Essami

Well-known member
Hi,

This is pretty weird that I notice this only now. But I was shooting a starry sky so it was more obvious then on any other shoot I've done. It seems that the infinity focus on my Canon FD lenses is off. I need to adjust the focus ring a little back from full infinity focus to get perfect infinity focus.

Has anyone else noticed this who is using non 4/3rd lenses?

Sami
 
This is normal. Tolerances for the optical distances are so narrow that adapters and especially slightly worn lenses can not maintain them. Micro focusing would be needed on the sensor. Hence the adapter is made so that you certainly get infinity, even if it goes a little beyond. How much it goes beyond depends on the lens, lens sample (i.e. how worn the lens is) and the adapter. The actual difference in distance for the lens elements in meters is micro meters, not easily maintainable by manufacturing tolerances. Even temperature change could change the location of infinity. Some lenses could be adjusted for this but it requires disassembling the lens and then testing to see whether infinity snaps to it's proper place. If it didn't, one has to do it again, which can be laborous.
 
I'm using some old Nikon E primes and they go a bit beyong infitiny. Strange thing is that this problem only occurs at f2.8 (wideopen on my 28mm) but if I'm at f4-5,6 the infitiny focus is sharp and nice.
 
Thanks for the answers, very useful to know this! A few times I've cursed the fact that some wide nature shots have been slightly soft. Now I know that I need to always focus, even if shooting distant landscapes.
 
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