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Re: [OM] DoF Compared

Subject: Re: [OM] DoF Compared
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Tue, 10 Aug 2010 22:45:42 -0400
I finally realized what I was driving at in the comments about viewing 
the image at 1/4, 1/3 and 1/2 life size and that has to do with 
resolution of the LCD on the camera during live view at 10X.  If the 
camera isn't actually taking you to full pixel view but rather to just 
1/2 of that then the difference *while focusing* between the left and 
right images in AG's 3rd page is not visible on the focusing screen.

Chuck Norcutt


Chuck Norcutt wrote:
> 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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