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[OM] Re: A couple of Velvia 50 birds

Subject: [OM] Re: A couple of Velvia 50 birds
From: Moose <olymoose@xxxxxxxxx>
Date: Tue, 10 Jun 2008 02:53:32 -0700
C.H.Ling wrote:
> ----- Original Message ----- 
> From: "Moose"
>
>   
>>> I'm comparing different lenses on the same 4/3 body, the best one will 
>>> still be the best in FF
>>>       
>> I think this is not always true in the digital realm, with digital 
>> resolution and anti-alias filters. I believe it is possible for a lens to 
>> "out resolve" the sensor system on a large sensor, but be "out
>> resolved" by a small senor system. If another lens out resolves both 
>> systems, it will equal the first lens on FF, but be superior on 4/3.
>>     
> Haven't seen such a lens yet, the best in 4/3 is still the best in 40D, I'm 
> talking about center resolution, I know there could be edges performance 
> difference. 
My mistake, I should have typed APS-C, not 4/3. I was really talking 
about Ff vs all of the smaller sensors. I wouldn't expect much 
difference from 4/3 to APS.
> I will try FF Canyon later as I heard the new FF is coming soon at $2000 
> range, but I will not do it on film anymore there is just too many factors 
> affecting the result.
>   
Hey! No fair. :-)
> I mean for this comparison (bird shots), subject is close to center.
>   
Fair enough.
>> ......
> We are talking about net optical performance, not field performance. 
I'm not sure what you mean by "net optical performance". May be a 
language difficulty (Not a complaint!, My Chinese is much worse than 
your English.). To me, net means what's left after all "deductions", and 
so would be actual performance in practical use, as opposed to 
performance under ideal conditions, which would be the "pure" optical 
qualities of the lens.

In any case, field performance is what matters to me. Still, ideal tests 
show the upper limits of the possible with any lens.
> Anyway, in my experience the field performance can reflect the net 
> performance very well, like the 200/4 case, I just feel 180/2.8 is better 
> even in the film age.
>   
I think your test shots show the resolution edge of the 180 over 200, 
although it appears to be very small to me. They also show the 180 with 
a modest contrast edge. Combined, those two definitely make the 180 
appear sharper, and that would be a big advantage with film, especially 
before scanning.
>> .............
>> It's hard for me to imagine an application in which I would use either
>> lens where such small differences in resolution would be significant. I
>> understand that apparent sharpness differs by more than the actual
>> resolution difference. The 200 obviously has lower contrast. However,
>> that's not the issue, at least to me, that it was in the film era.
>>     
> The better in contrast (MTF low and high frequency) is very useful, pull up 
> the contrast will increase the noise/grain. More important is the better one 
> will resolve some low contrast details while the other one may just lost 
> them. The difference may not be very significant to you but it is there.
>   
Well, it's not a practical issue for me, as I only have one of the 
lenses, and don't see myself acquiring a 180/2.8

Moose

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