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Re: [OM] DoF Compared

Subject: Re: [OM] DoF Compared
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Tue, 10 Aug 2010 22:30:42 -0400
You're getting closer to convincing me.  The background is certainly 
sharper on the PanaLeica side of the fence but I still have to be 
convinced that both lenses were focused at the same distance.  The lens 
differences at the edges of the field make that difficult to determine. 
  I still say show me two high contrast targets at 5 and 5.5 meters with 
one in and the other out of focus.

I don't know what it means but found it interesting to compare these 
images at 1/3 life size.  My informal sharpening rules say to display 
the image at 25-30 percent of its cropped and resized, full pixel size 
in order to simulate what it will look like on a print.  At 1/3 life 
size the difference between left and right disappears and is even hard 
to discern at 1/2 life size.

Chuck Norcutt


Ken Norton wrote:
> OK, I added a third page to the article. The entire vertical portion
> of the center of the images are compared side-by-side. I did reprocess
> the images to address some issues in the process of converting
> Panasonic raw files and also adjusted the contrast to better match the
> two images to cover for the way one thinks something is sharper
> because it is contrastier.
> 
> It does appear that the Zuiko shot is focused slightly closer, but not
> by much. Definitely not enough to explain the top portion of the
> image. I will admit, though, that in this example we see more issues
> with the 24mm lens with the curved plane of focus which does rear its
> ugly head at F4.
> 
> As I mentioned before, over lunch I did retest with closer subjects. I
> can find reasons why these test images can be criticized, but I'm
> convinced that the test is repeatable.
> 
> AG
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