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Re: [OM] Zuiko 100 F2 does flowers

Subject: Re: [OM] Zuiko 100 F2 does flowers
From: "Carlos J. Santisteban" <zuiko21@xxxxxxxxx>
Date: Thu, 1 Sep 2011 01:05:04 +0200
Hi Chuck, Ken, Fernando and all,

On Mon, Aug 22, 2011 at 8:19 AM, Ken Norton <ken@xxxxxxxxxxx> wrote:
> It's actually the other way around. A smaller sensor places a much greater
> demand on the lens.

Chuck wrote:
> True, but a well made 35mm lens such as the Zuiko 100/2 has very few
> sins of any sort in the central portion of the image.

From: Fernando Gonzalez Gentile <fgonzalezgentile@xxxxxxxxx>
>Carlos Santisteban made lots of comparison tests using a fourthirds
>sensor, and I doubt he fooled himself.

Hey, that's an _explicit_ allusion :-) :-) I think you all are right... but
read below for details:

Ken Norton <ken@xxxxxxxxxxx> wrote:
>Some stuff can be determined through using a crop-sensor camera,
>the rest through film.

With "critical" lenses I usually make a second test with film ;-)

>What most don't realize is that when you look at
>the corners of an 4/3 image, you're actually quite a ways to the edge
>of a full-frame and definitely hitting the point where the optics
>start falling apart.

Certainly. According to Seidel's Sums, some aberrations (spherical,
logitudinal CA) keep constant across the *whole* frame, some others (lateral
colour, coma) increase proportionally to the angular field, and others
(astigmatism and field curvature) depend on the *square* of the angle... but
can be easily extrapolated by looking at several points on the cropped
image.

>Very
>few lenses are good across the majority of the image area and then
>fall apart only at the margins.

Yes, I think so. Some aberrations may be less predictable, mostly mechanical
vignetting and distortion, but I care less about them. In case of doubt,
there's always film...

Incidentally, I'm testing a borrowed Zuiko 100/2. I know I *will* be flamed
by this but, so far, it hasn't impressed me... The previous, technical test
(on M4/3) showed up good performance, but not as stellar as the Macro 90/2,
at least within far subjects. Having into account other practical issues, I
can't justify purchasing one:

-The (much loved) 85/2 is fast and compact, but no-so-sharp wide open,
although it's great from f/4. Sometimes that's an advantage ;-) There is,
however, notable performance (and style!) difference between versions --
I've got three of them (silvernosed, MC and 'Zuiko')

-The (silvernosed) 100/2.8 is equally compact and definitely sharper at max
aperture, but it loses a full stop for a negligible focal length increase
:-(

-The 100/2 is bigger, but still easily handed. It's fast and has pretty
decent performance wide open, although not as good as...

-The Macro 90/2 bears impressive optics with beautiful, 'snappy' rendering,
but *awful* ergonomics :-(

Maybe the tested 100/2 is a bad copy, or simply difficult to focus on the
GF1... anyway, I did a 'real world' test on film, comparing it to the latest
85/2: <
http://www.flickr.com/photos/zuiko21/6043396265/sizes/l/in/set-72157627310503393/>
;-) The rolls are awaiting development, along with the holiday shots. I'll
let you know...

Cheers,
-- 
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
-- 
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