Re: [Leica] autofocus macro

[Henning Wulff <henningw@archiphoto.com>]

At 1:36 PM -0500 5/1/01, lea wrote:
>I see what you mean. Yours seems to be the reason so many are not 
>using it. I simply
>recompose.
>
>Lea
>
>Isaac Crawford wrote:
>
>>  lea wrote:
>>  >
>>  > <<(and remember that, if your main purpose is macro photography, 
>>autofocus is of
>>  > very little use at all),>>
>>  >
>>  > This is the second time in a week (maybe 2) that I've seen a 
>>statement like this.
>>  > Could someone explain WHY autofocus macro isn't of use. I use it all the
>>  > time...from 35mm to 645 and you couldn't pay me to give it up.
>>  >
>>  > Perhaps the statement comes from people doing a different type 
>>of macro work than
>>  > what I do?
>>  > Lea
>>
>>          At "true" macro ranges (i.e. 1:1 or maybe even 1:2), the camera
>>  inevitably picks the wrong thing to focus on. Since DOF is so shallow,
>>  and the subject (usually) fills the frame, there are many different
>>  places it could pick, but only the photographer knows which is the right
>>  one...
>>
>>  Isaac
>>  >

Another reason why AF doesn't work with macro is that a slight change 
in focussing distance makes a big difference in the reproduction 
scale, especially at 1:1. I usually frame and set the reproduction 
ratio first, then move back and forth to focus. AF doesn't allow 
that. Actually, right at 1:1, focussing using the helicoid (or AF) 
doesn't work at all, only the reproduction ratio changes. The 100/2.8 
USM lens is a very good lens, and I use it for a lot of macro stuff 
with the MR14 ringlight, but in macro it stays in manual focus. Same 
for any macro lens I use. If the setup is on a tripod, I use a 
focussing rail.

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    *            Henning J. Wulff
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