Do either the 100/2.8 or 100/2 use a component of internal focussing ?
...Wayne
>
> 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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