Bernard Frangoulis wrote:
>> Choosing a lens so that you can actually take a photo at f/2.8 is a
>> different consideration than my use. I'd probably up the ISO several
>> notches before opening the aperture but that's something that will
>> likely kick off a whole separate discussion.
>>
>
> Chuck, one of the good points of ZD lenses is that they reach their optimal
> resolution (or nearly so) at full aperture.
Not just ZD, I think My reading of tests and personal experience is that
contemporary lens design and technology results in quite different
aperture/performance characteristics than for the older MF lenses. I
assume this is due to the increased use of higher and lower refractive
index elements and aspheric elements. Given the tools, designers aim for
optimum performance as close to wide open as possible.
Many current mid to high end zooms seem to have optimum apertures at or
near wide open. It used to be that you could be fairly sure that the
"sweet spot" of a lens would start about 3 stops down from wide open and
go for a couple of stops beyond. Now, the optimum aperture is usually
only a stop or so down and occasionally is wide open. And the sweet spot
is from wide open to seldom more than three stops down.
Moose
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