Before digging into full wave dof calculations vs thin lens
approximation and correspondence with Nasse at Zeiss,
would not have thought such a dof discrepancy
could be real. It seems very possible now. Real FL differences also
change the distribution of the dof, but don't know
the actual measured FL for each of the Zuikos and doubt they differ by
very much. First thought the differences
might be due to focus shift----see the demonstration below with the
Zeiss 85/1.4. Fast lenses of certain designs w/o floating elements
often shift focus stopping down. Dr. Nasse seems to get pinged on this
issue a bunch.
http://www.the-digital-picture.com/Reviews/Zeiss-85mm-f-1.4-ZE-Planar-Lens-Review.aspx
Then AG said he had focused at the shooting aperture, which
ruled that out.
Still, a similar set up with the Zuikos might easily resolve the
question unequivocally.
Would need to be cautious with the experimental design. Dr. Focus
appears to be around to help.
Anyway enjoyed the post.
Mike
When shot at exactly the same apertures, and carefully
> selecting the same focus point, the 100/2.8 always seems to have a
> touch
> more DoF on the near-side. At this time, I'm calling this a human
> error, yet
> time and again, when focused in exactly the same manner on exactly
> the same
> point, the 100/2.8 is sharper closer in. I've even focused the lenses
> stopped down and the same thing occurs. Before letting this go,
> totally,
> what I'm wondering is whether or not the rate of defocus either side
> of the
> plane of focus is assymitrical between the two lenses.
--
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