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Re: [OM] A wasted effort

Subject: Re: [OM] A wasted effort
From: Moose <olymoose@xxxxxxxxx>
Date: Tue, 17 Mar 2009 01:53:02 -0700
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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