A slower lens will help a little but this is not the key. Fine calibration
is required if you wanted to ensure no focus shift during zooming. I
calibrated many Zuiko zooms (and also the two Tamrons I just acquired) in
order to ensure the focus does not change during zooming, this is more
critical for the wide zooms.
I suspected the modern AF lenses are more difficult to ensure for this
aspect as the AF mechanism (lens element group) need some space for movement
(can't be too tight). I see some lenses even have different sharpness from
left to right side, this including a Tamron 28-300mm, DZ 11-22mm, Tarmon
24-135mm, DZ 14-42mm. I also heard some stories about the poor quality
control/standard of Canyon, people keep purchasing the lens until they found
a best one, the rest just sell it out.
C.H.Ling
----- Original Message -----
From: "AS"
>
> Would this depend on how fast/bright the lens is? i.e., f4.5 - 5.6 zooms
> will be worse than say constant F2.8 zooms?
>
>
>
>> I agree with you all modern zoom
>> lenses do not adjust focuse distance with
>> zooming but not all of them maintain focus either, try your
>> Canyon zooms,
>> they only calibrated at the long end.
>>
--
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