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Archive 2009 · what is focus by wire?
  
 
lamonica66
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p.1 #1 · what is focus by wire?


I notice that many reviews on the canon 85 1.2 L state that one downside is focus by wire..

What is it, and why does it stink, if it does?
Thanks as always.


Matt



Mar 04, 2009 at 06:37 PM
Greg Feldman
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p.1 #2 · what is focus by wire?


Normally, the focus ring is mechanically coupled to some of the lens elements, and turning the ring moves the glass.

Focus by wire is a lot like "drive by wire" where the gas pedal is not mechanically coupled to the engine but instead is an electronic switch that tells a computer how much gas to toss into the engine. In focus by wire, the focus ring is not mechanically coupled to the glass. It's just an input device like an old Atari paddle that tells a computer to go ahead and move the glass elements.

It doesn't necessarily stink, but it feels a little weird and you can't retract the front element unless the camera is turned on.



Mar 04, 2009 at 06:43 PM
Geofn
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p.1 #3 · what is focus by wire?


The manual focus ring is not physically coupled with the focusing mechanism. Rather, rotating the ring sends an electronic signal to the focusing mechanism. In practice, this means that the lens must be mounted on a camera body (and therefor receiving power) in order to change the focus. No big deal, really. And the manual focus ring has a very "loose" feel to it, more like a lack of resistance, compared to other lenses.


Mar 04, 2009 at 06:44 PM
WmPat
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p.1 #4 · what is focus by wire?


Focus by wire means a system where your turning of the focus ring actuates an electric motor that moves the glass elements of the lens to the proper position to achieve sharp focus. The alternative is a mechanical system where your turning of the focus ring moves the elements directly. Perhaps people say it stinks because it is not as fast or precise as mechanical focusing. That may be true for some Focus by Wire systems but the more advanced ones have 2 or 3 user-selectable speeds and can work very well. It's not a big deal for those of us who rely on Auto Focus most of the time.


Mar 04, 2009 at 06:51 PM
Alistair Watson
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p.1 #5 · what is focus by wire?


The downside is usually because people associate 'focus by wire' with a slowness to focus. Case in point is the 85/1.2 L. Focus is very accurate but the image doesn't snap into focus say like an 85/1.8.
I never thought of the 85L as a sports lens and never tried to use it as such.



Mar 04, 2009 at 07:01 PM
 

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mattbradders
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p.1 #6 · what is focus by wire?


There does seem to be some negativity about focus by wire - I have to say, I don't get it, the manual focus ring on the 85L is soooooo smooth it's sexy.


Mar 04, 2009 at 07:11 PM
lamonica66
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p.1 #7 · what is focus by wire?


Thanks to all!

You all rock....



Mar 04, 2009 at 08:12 PM
Lord Fluff
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p.1 #8 · what is focus by wire?


Alistair Watson wrote:
The downside is usually because people associate 'focus by wire' with a slowness to focus.


Indeed - yet the 200/1.8 has it and that's no slouch....



Mar 04, 2009 at 08:37 PM
Leeuwtje
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p.1 #9 · what is focus by wire?


I like the feeling!


Mar 04, 2009 at 08:42 PM
joezasada
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p.1 #10 · what is focus by wire?


the 85L isn't slow... it's precise... it's a lot more of a turn to move through the focus range than say... a 16-35L... think of it as a more fine-toothed gear...

the focus by wire works great for me... very smooth, and very precise.... once you get used to it!



Mar 04, 2009 at 10:46 PM





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