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Metabones, Canon EF lenses and Direct Manual Focus mode


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among the restrictions of the Canon EF lens adapter for Sony E-mount cameras, Metabones lists "Direct Manual Focus mode (DMF) not supported". When I sent them an email, the reply was they had no intention of implementing that feature.


Since I don't have an alpha yet, I'm a bit confused what DMF actually is and what that restriction means.

What I'd want from the camera is what Canon calls "Full Time Manual" (FTM), which is a feature of their "genuine-USM" powered lenses. It means that you can manually focus at any time, regardless of the setting of the AF switch on the lens.


I find this feature critical. If you combine it with a configuration where a shutter half-press does no longer start the autofocusing but you have a separate button for the AF start, this the lets you focus manually but press the AF button whenever you feel like it. You'll never have an annoying accidental re-focus occur when all you wanted was measure exposure.


I would be very glad if any Sony/Metabones users could confirm if that works with Canon EF lenses on the adapter or not.


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That should work. The Canon FTM is not actually

a "built-in" or "additional" feature. Whenever you

use FTM while in AF mode, you are just "forcing"

the focusing mechanism. The Metabones adapter

doesn't need to know you are doing that, and it

has no way of knowing it either. Suppose you put

your eyeglasses over the front lens element, which

would refocus the image .... the Metabones again

won't know, can't know, and doesn't need to know.


You can also force some non-ultrasonic lenses in

the same manner. The important difference is that

after you do this a few times to the non-USM lens

you may have damaged it. The USM drive lacks

a solid mechanical coupling. So, when you force it

you're not really "forcing" a gear train or any other

moving part. The "mechanical coupling" of a USM

is not a gear train or such. The coupling medium

is simply air. And when that air is not activated into

sonic waves, the focus ceases rotating. But it's OK

to rotate it manually. You won't damage the air.


The Alpha "DMF" relies on Sony's system where

the focus ring is NOT mechanically coupled but

is simply a data wheel ["fly by wire focus"]. I don't

see why Metabones even mentions "DMF" when

describing functionality of adapted Canon lenses.



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