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Old 14-01-2011, 01:56 PM
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dugnsuz (Doug)
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Min Focus Distance Switch on Canon Lenses

Hi all,
A tech' question for Canon lens buffs regarding the Minimum focusing distance switch on Canon lenses

In terms of the optical train - does switching from the 1.2m-infinity to 3m-infinity settings introduce (or remove) any extra optical elements?
Doesn't sound like anything happens mechanically inside the lens when it's switched


Thinking the less glass in the way of the stars the better!

Doug
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Old 14-01-2011, 02:15 PM
Dennis
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Hi Doug

I think that setting the switch to operate within a limited range helps the AF work faster. That is, when you set it to 3m to infinity, it doesn’t try to go rack the AF all the way down to the minimum focus distance when attempting to AF the lens.

By restricting the range to cover only your specified region of interest, the AF should then home in on the correct focus plane quickly without having to exercise itself over the whole design range.

Cheers

Dennis
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Old 14-01-2011, 03:21 PM
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Octane (Humayun)
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I think it's purely a software restriction, Doug.

H
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Old 14-01-2011, 04:20 PM
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dugnsuz (Doug)
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Thanks D+H - makes sense.
Doug
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