Johnny Johnson wrote:
> At 07:43 AM 7/24/2007, Chuck Norcutt wrote:
>> While I'm sure Johnny is correct
>> about the better glass being able to handle 22 MP I've seen it reported
>> that some of the wide angle glass can't handle the 13-16 MP of the
>> existing bodies, at least at the edges.
>>
> Heck, even wide Leica glass is softer in the corners than the center
> of the frame, especially when shot wide open and I don't think it
> takes a very high resolution capture medium to show that. But, I
> wonder if what you said above is entirely true. Just because there's
> less resolution at the edges of a 16mp capture that at the center
> doesn't necessarily mean that the lens has topped out does it?
It seems to me that at least three different things are be mixed up here.
1. Yes, most lenses are at least slightly less sharp in the corners than
in the center with film. And this may be generally more true with super
wides. However, it's only a generalization. The Zuiko 18/3.5, for
example is not that way. Gary said in his film based test. "lens design
emphasizes outer zones at expense of center image zone (which gives a
sharper overall impression of an image)". Mike H's tests of it against
other MF lenses on FF Canyons came to much the same conclusion, Zuiko
competitive in the center, and stomps the rest in the corners.
2. There is a sensor issue with conventional wide angle lenses because
of the way light reaching the sensor at any angle much beyond 90 degrees
interacts with the physical aspects of the photosites. Even a lens with
equal sharpness across the whole frame on film, but which is not
telecentric (i.e. all conventional WAs), will have problems in the
corners with all of todays FF sensors.
3. Leica and Kodak have come up with a useful design that minimizes this
problem by offsetting the micro-lenses, illustrated here.
http://www.dpreview.com/articles/leicam8/
HOWEVER, that was not enough, as the review points out. Leica also uses
a 1.3x sensor, 27x18 mm in size. So they also simply throw away those
troublesome corners. They do, of course, have an even worse problem than
do SLR makers, as their widest lenses, not needing to clear a mirror,
get even closer to the film/sensor, and have even more acute angles of
light reaching the corners of the frame. One of the classic advantages
of a rangefinder for WA ends up being a disadvantage for digital.
So, any discussion of WAs and sensors which doesn't at least acknowledge
that it's not just a lens problem, is likely to be misleading. Sure,
Canyon's WA lenses may be less wonderful than other makes, but we don't
really know that. Nobody else's recent AF lenses for film cameras have
been subjected to the scrutiny and problems of FF sensors.
I was not aware of anything about Canyon WA lenses before digital, but
what I've run into since suggests that film users weren't of the opinion
that they were inferior to other makes.
Is it the Lens? Is it the Sensor?
Moose
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