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[OM] Re: A couple of Velvia 50 birds

Subject: [OM] Re: A couple of Velvia 50 birds
From: "C.H.Ling" <ch_photo@xxxxxxxxxxxxx>
Date: Tue, 10 Jun 2008 10:20:07 +0800

----- 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. 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.

>> (at least the center, that matter more in this comparison).
>>
> Again, I disagree. The center may matter more for some subjects and
> uses, and not for others. According to Gary, the 18/3.5 "... lens design
> emphasizes outer zones at expense of center image zone (which gives a
> sharper overall impression of an image)"
>

I mean for this comparison (bird shots), subject is close to center.

>> BTW, high speed flash illumination will eliminate all vibration problem.
>>
> Of course. And if one is only going to shoot with flash, there's no
> problem. I almost never use flash and the images that started this all
> didn't either. If Gary had used flash, his tests would indeed only have
> tested the pure optical quality of the lenses. How much more useful to
> have practical tests that show what real world problems the lens/camera
> combinations have and solutions to minimize the problems.
>

We are talking about net optical performance, not field performance. 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.

>.............
> 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.

C.H.Ling




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