Re: [Leica] Monaghan's thought on AF lenses

["Robert G. Stevens" <robsteve@hfx.andara.com>]

Dan:

Perhaps the problem for autofocus is to focus where there is lots of depth
of field like the typica f4-5.6 zoom.  The sensors measure contrast to
determine focus and are probably accurate with fast lenses, but less so
with slower lenses.  For example, I can focus my 180mm APO Summicron really
fast because it is either in or out of focus because of its shallow depth
of field.  I cannot focus the 105-280 zoom as quicly because the crossover
from in focus to out of focus is not as distinct.  

Perhaps Erwin can give his thought on this?

Regards,

Robert

At 04:49 PM 8/22/99 -0400, you wrote:
>I am not sure how meaningful that Popular Photography article is.  I have
>taken many photographs using autofocus cameras and telephoto lenses with
>very shallow DOF where the focus is precisely where I expected it to be
>(usually the eyelash of a model).  If there was any 'real' innacuracy
>inherent to autofocus, I am sure I would have noticed many shots where the
>focus ended up on the ear, or node or somehwre else.  Perhaps on an optical
>bench a manually focused lens will outperform an autofocused lens, but I
>just never notice it in practice.  In fact, I autofocus continues to amaze
>me as to how well it works.
>
>I think this is another example of how dangerous a little knowledge can be
>in the wrong hands.
>
>Dan C.
>
>At 10:42 PM 22-08-99 +0200, you wrote:
>>In a recent post, Robert Monaghan writes :
>>(...)
>> "As for the sharpness mania, do you realize that most autofocus lenses
>>deliver far less critical sharpness in practice than a carefully focused
>>manual lens (again, per PopPhoto and other tests)? If you are a serious
>>amateur photographer, why are you paying three to ten times more for
>>autofocus lenses
>>that are far worse in practice than your older manual focus lenses? Duh? "
>>(...)
>>I'm surprised because it is the first time I read such an argument.
>>True or false ?
>>
>>Dominique Pellissier
>>
>>
>>
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