I had to re-read Merklinger's article which I see I first read and saved
in 2007. The problem I have with Merklinger's article is that he
discredits standard hyperfocal methods (as below) by noting the
resolution gains by focusing at distance X vs distance Y. However, he
doesn't point out that a 6 fold increase in resolution at distance X is
unusable if you're not making a print large enough to call for it.
The whole idea of depth of field and hyperfocal methods is starting from
a given size circle of confusion which already assumes a maximum print
size, viewing distance and resolution of the human eye (forgetting the
Moose, of course). The point is that, done right from the start, if you
need a 6 fold increase in resolution that should already have been
factored into your calculations. If you don't need that there's no
reason to sacrifice the resolution at point Y to gain the 6X resolution
that was never planned for or needed in the first place.
I did note some interesting examples: For example, he wanted a train
engine in the foreground to be sharp but also wanted individual stones
in the train station walls in the near background to be resolved. That
was an admirable application of his math and a very good example of
something you *might* want to do. But in today's digital world vs the
film world he was familiar with I would probably just take a couple of
exposures at different apertures and use the E-M1's 14X magnification to
see if any of those apertures has solved the problem.
I think he might write a much different book today if it was centered on
digital photography. One other thing I had a problem with was talking
of circles of confusion of 1/200mm. In the real world, getting
resolution that high is a lab exercise with a tripod mounted on a 500
pound block of concrete. And especially difficult with film since few
films can resolve that kind of detail.
Chuck Norcutt
On 1/31/2016 10:46 PM, Mike Gordon via olympus wrote:
It clearly depends on the image and the importance of critical
sharpness at different distances. Recall from Merklinger's
article that by focusing at infinity one gains 6 fold increase in
resolution for distant objects and only loses 2X at the near limit of
DOF.
http://www.trenholm.org/hmmerk/TIAOOFe.pdf (about page 32)
One easy solution, if circumstances permit, is to focus stack at a
wider aperture and eliminate the compromise (but introducing
others).
Now I know it is really mid-winter with a diffraction/dof thread,
Mike
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