Ken Norton wrote:
>
> I know exactly what diffraction limits are and definitely see the results in
> all lens tests that I've done. However, I think what both CH and I am saying
> is that we won't let math stand in the way of getting a picture not possible
> by being a slave to numbers.
I agree there. I think it is useful to know the technical limits, but
not useful to let them get in the way. Otherwise, how could I use my
cheap, shoddy Tamrons for most of my photography. For me, they are far
more likely to get the shot than more zooms or a bag full of primes to
cover the same range.
> I looked at your excellent rollover comparison.
Thanks. I often find it hard to really compare images for fairly subtle
effects any way but superimposed.
> The sharpened F22 image is awefully close to the F4 image. Had it not been
> labeled, I would have been hard pressed to identify one over the other except
> for the presence of the sharpened JPEG artifacts. TIFF files
> would have been nearly impossible to identify.
>
I was a little sloppy with the sharpening, as I was mostly trying to
show how sharpening may bring up detail. Were it my image and were I
planning to print it wall size, I'd have been more careful and subtle. :-)
Working with the two original, full size JPEGs, the f4 image is subtly,
but clearly cleaner and more detailed.
>
> What I find odd is the methodology for evaluating 'the best "walk about"
> wide-angle' for a full frame body.
>
> No doubt. I suspected that I'd get some grief over the center-only
> resolution testing.
Not really grief, just questions.
> Traditional testing checks at least center and somewhere out near
> the edge. ...
>
>
> This is also true with my MC 24/2.8, but the gain near the fringe is not
> enough to cover up the fact that the center is soft wide-open.
>
>
> If I had the results of this test, I'd still be uncertain how they
>
>> If I had the results of this test, I'd still be uncertain how they pertained
>> to the question of comparative individual overall lens resolution on FF. I
>> can see your dilemma, given the lack of a FF DSLR
>> and the considerable additional time and cost of doing a film based test.
>> Still, it does look suspiciously like "wasted effort" to me.
>
> Well, another factor is that this test is for my specific set of lenses. To
> perform a completely valid test we should probably have a sampling of at
> least five lenses of each type. This way it would take into account
> manufacturing variances.
>
I wasn't really heading in that direction. I suppose it's just that if
I'd gone to that trouble, I'd have had at least a couple more targets.
Even if I didn't use them at the moment, I"d have the shots if/when I
got curious about mid distance performance.
> The E-1 has greater pixel density than the 5D. 2MP per cm2 vs 1.5MP per cm2.
> Granted, the 5D has a weaker AA filter which improves things quite a bit, but
> since these lenses are exceeding the ability of 2MP per cm2 to
> resolve to the extinction point, the 5D won't tell me anything more about
> center sharpness than what I am already getting--and I'm not getting enough.
>
I'm not sure about that. The 5D has better, for want of a better term,
"per pixel sharpness" and might well resolve as well in practice as an E-1.
> The 5D, though, would give me resolution data at the corner of a 35mm frame.
>
But that's really what I was suggesting.
> .... What is bothersome for this test on film is that I still have more
> detail on the negative in the test charts than is scannable at 4000dpi.
I have no idea whether this would be true of your Nikon. I have found,
mostly by accident, that multiple passes with the Canon actually
increases resolution of detail.
> ... Maybe I'll get a brick of that Efke 25 or something for full-frame
> resolution testing....
>
Wasted effort. Go take pictures!
Moose
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