I have to admit that I hadn't thought about pixel diffraction but I
doubt that's the cause of the warnings for upper aperture range. I just
checked every single digital Zuiko and every one of them (including the
8mm) closes down to f/22... a stop smaller than a good many Zuikos of
the same focal length. I doubt that Oly has any magic to prevent pixel
diffraction.
I don't understand what you were driving at with the comment about
programmed modes.
Chuck Norcutt
Winsor Crosby wrote:
> I don't know. It may be a combination of considerations for image
> quality. Wide open fast lenses designed without the parallel ray
> considerations that Olympus finds so important may restrict one end of
> the aperture range. At the other end with smaller apertures and the
> small pixels used by Olympus you run into pixel diffraction much
> sooner than the aperture diffraction that you see in Gary's tests.
> While pixel diffraction would be present in any lens at moderately
> small stops on an Olympus digital camera, Olympus may feel that
> because an OM lens must be operated manually it requires a special
> warning compared to lenses that can operate in programmed modes on the
> camera.
>
>
>
> Winsor
> Long Beach, California, USA
>
>
>
>
> On / November 11, 2007 CE, at 6:54 AM, Chuck Norcutt wrote:
>
>> However, I've just convinced myself that it only has to do with
>> metering. I haven't done all of them (only up through all the
>> primes or
>> zooms starting at 50mm or less) but Oly's recommended aperture ranges
>> for the lenses I checked have a very poor correspondence with optimal
>> performance as shown in Gary's lens tests. Optimal resolution and
>> contrast on Gary's tests are very often achieved at apertures smaller
>> than Oly's recommendations and, on rarer occasion, larger. There
>> are a
>> few which do correspond fairly well but, for the most part, no. For
>> best optical performance I think you need to pay attention to Gary and
>> ignore Oly's advice.
>
>
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