On 10 Aug 2010, at 2:32 PM, Chuck Norcutt wrote:
> I'm afraid I'm not yet convinced. There are two compounding factors
> not
> controlled for.
<snip>
Ken, I unfortunately agree, I am not convinced. I agree that the
"character" of the
blurred regions can be different between lenses, but I don't think one
can
ignore:
* Light rays travel in straight lines towards the entry pupil of a lens.
* All lenses at 24mm and f/4 have an entry pupil of identical area,
otherwise they are incorrectly marked.
* Light rays travel in straight lines from the exit pupil of the lens
to the recording medium (e.g. film plane).
* In both 24mm retrofocus lenses you have used here, there is a good
chance
that the exit pupil - to - sensor distance is quite similar (not
that it
matters in determining DOF, but it just might, who knows).
Assuming the above, I have to assume that the circles of confusion
must have the
same basic area in both lenses, regardless of the fact that one may
have a better
"gradient" within those circles to present smoother bokeh, or that one
lens may
actually be sharper in the in-focus are than the other.
I don't want to question your testing methods outright, but by looking
at your
crops, I get the distinct impression that the OM Zuiko lens is focused
closer
than the Panasonic/Leica one - i.e. the in-focus area of both do not
have the
same crispness.
There may be other explanations, but like Chuck, I am firmly in the
"not convinced"
camp as well.
Dawid
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