I recently bought an old book entitled "Image Clarity" with a sub-title
of "High Resolution Photography" by John B. Williams, Focal Press 1990.
I just got it a couple days ago so certainly haven't read it much
beyond skimming the contents. But I did take note of the last couple
pages which are a section titled "Diminishing Returns".
In that section he supposes a hypothetical camera/lens/film system
capable of resolving 100 lines/mm or what he calls "a system of superb
quality". But in the hands of a rank amateur with no photographic
training the likely result will be no better than 5-10 lines/mm. In the
hands of an experienced photographer (working hand held) typical results
will be about 20 lines/mm and with very careful technique (such as Ken's
"between heartbeats") hand held results may reach 40 lines/mm. The same
experienced photographer working on a tripod may routinely reach 80
lines/mm but many photographs will not. Camera motion (even on the
tripod) will be one but not the only reason for failing to get above 80
lines/mm. Lens faults, diffraction, focusing errors, micro vibrations
within the camera, ground vibrations on long exposures will all play a
part. With extraordinary care and massive camera support, careful lens
and aperture selection, extreme care in focusing, etc. it may be
possible to achieve 95 lines/mm in field work. In the studio with even
greater control it may be possible to reach 98 lines/mm... but not
necessarily consistently.
Ignoring the problems of Bayer array interpolation, a 12.7 MP Canon 5D
sensor can resolve about 60 lines/mm. Allowing for the Bayer array it's
something less than that. Proportional to the 5D sensor, 40 lines/mm
for the very careful hand held photographer equates to about 6 MP... a
number I quoted the other day from another source.
Chuck Norcutt
On 9/9/2011 11:46 PM, C.H.Ling wrote:
>
> ----- Original Message -----
> From: "Ken Norton"<ken@xxxxxxxxxxx>
>
>
>>> The live view magnifier on the 60D is starting to convince me that a lot
>>> of softness that I've put down to other factors
>>> over the years has been less than perfect focus.
>>
>> Exactimundo! The two killers for me is camera/subject motion and focus
>> imperfections.
>
> Same here, I have been knowning myself a non stable shooter for a long time
> and found out AF can be inaccurate since using the E-1.
>
>> The problem for me is that focus imperfections are
>> addressable by closing the lens down. camera/subject motion is
>> addressably by opening the lens up.
>>
>
> To me the solution for camera motions is a camera that shoot high ISO with
> beautiful image quality, 5D II do help some.
>
> Aperture is mainly for DOF control, it is so poor if it fall to use as focus
> error compensation. The OM viewfinder with Minolta Acute Mate focusing
> screen is close to perfect but not available to any DSLR :-)
>
>> I don't believe that emperical evidence supports the claim that
>> "...any handheld camera used at an exposure of longer than 1/1000 s
>> isn't going to resolve mroe than about 6 Mpix in any case, reagardless
>> of the lens or sensor used."
>
> My expression will be shutter speed of 1/focal length is far not enough for
> maximum image quality. It also vary with camera body and lens, the worse
> combination for me is 5D II with OM 200/4. Last time I shot 5 images to get
> a perfect one at 1/640s handheld.
>
> C.H.Ling
>
--
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