I would certainly choose the 105 based on working distance. Whether f/2
vs 2.8 is an issue is hard to say. Guess it depends on what and where
you intend to shoot. But if you're talking OM gear and bellows the
bellows is calibrated for 50mm and not for 105. Maybe that would make a
difference to someone.
Even though both have the same DOF at equivalent apertures and
magnification I was thinking that the 105 might ultimately be more
preferable for DOF if the larger lens diameter allowed a smaller
aperture to be used before diffraction limits set in. In searching for
the answer to this I discovered the previously unknown to me phenomenon
of diffraction at the pixel sites on the sensor. Make perfect sense
given that diffraction is caused by light bending around *any* edge
(including the lens mounting cell) but I hadn't stopped to think about
it before.
Interestingly, the 8MP 4/3 sensors are diffraction limited beyond f/5.6
and the 5D sensor is diffraction limited beyond f/11. I never got to
the point of trying to examine whether the 105 could handle f/22, for
example, and the 50 only f/16.
So I ain't so smart yet.
Chuck Norcutt
Moose wrote:
> Chuck Norcutt wrote:
>> If you have the same image size on the sensor from two different focal
>> lengths both images will have exactly the same depth of field at the
>> same aperture.
>>
> Thanks to Dr. Focus. I rather thought that was the case, but didn't feel
> confident stating it without calculation confirmation.
>
> So in the case of a choice between 50/2 and 105/2.8, DOF is not an
> issue, only viewfinder brightness vs. working distance.
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