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12/05/2006 12:15:16 PM · #1 |
| I'm pretty sure I've read in a number of places, possibly even in the TC instruction manual which I don't have handy, that center-point autofocus is all that will work when you've got a 1.4x TC on your lense. Yet this weekend I went out and bought a 1.4 and tried it on my 70-200 F4L as well as a friends Sigma 100-300 APO. With the tc on both lenses I was successful in using all AF points for focusing. Am I missing something? |
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12/05/2006 12:17:08 PM · #2 |
You will have AF with all points up to f/5.6. That means that your f/4 lens + 1.4xTC combination will AF with all points.
I think you're thinking about the "precision mode" of the center point, which only works with f/2.8 and faster combinations. |
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12/05/2006 12:22:12 PM · #3 |
Is this what you read?
If the EF 70-200mm f/2.8L USM lens is attached to an EOS camera having multiple focusing points and an Extender is attached to the lens, only the center focusing point will be usable for AF.
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12/05/2006 12:32:55 PM · #4 |
BTW, which TC? If it's a 3rd party TC, the camera may not understand that a TC is present.
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12/05/2006 12:38:56 PM · #5 |
Originally posted by NstiG8tr:
If the EF 70-200mm f/2.8L USM lens is attached to an EOS camera having multiple focusing points and an Extender is attached to the lens, only the center focusing point will be usable for AF. |
What's the source of this text? It seems to contradict known behavior.
I just now mounted my 70-200/2.8 and 2.0xII TC on the 5D body, and was able to lock focus on any selected point. |
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12/05/2006 12:50:43 PM · #6 |
I tried my friend's sigma 1.4x out and then when I saw a) it worked and b) did not cause any problems on my canon lenses I went and bought one.
I'm not sure exactly what I read but I'm fairly certain in both the manual for my F4L as well as the TC manual it said what Nstig8tr quoted. It doesn't seem to jibe with what the camera is actually capable of.
So all AF points will work up to 5.6. Good to know, thanks.
edit: same behavior using the sigma TC with the sigma lense.
Message edited by author 2006-12-05 12:51:24. |
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12/05/2006 12:56:55 PM · #7 |
Originally posted by kirbic:
Originally posted by NstiG8tr:
If the EF 70-200mm f/2.8L USM lens is attached to an EOS camera having multiple focusing points and an Extender is attached to the lens, only the center focusing point will be usable for AF. |
What's the source of this text? It seems to contradict known behavior.
I just now mounted my 70-200/2.8 and 2.0xII TC on the 5D body, and was able to lock focus on any selected point. |
A quick google turned it up here:
//www.bhphotovideo.com/FrameWork/charts/canon2xExtender.html
(which is talking about the 2x)
but not in many other places ...
linky
Message edited by author 2006-12-05 12:57:35. |
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12/05/2006 01:01:34 PM · #8 |
With the Sigma TC in place, does the camera report accurate EXIF information, i.e. correctly modified focal length and aperture? One quick way to tell is to see if you can still set the aperture to f/4, or if 5.6 is the lowest available setting. If you can still set f/4, the camera does not know the TC is in place. You are really at f/5.6, but the body still thinks it's at f/4.
When combining such a TC with an f/5.6 lens, the camera will still try to focus, even though the combination is f/8. AF may very well be successful, in good light and with higher contrast subjects.
Canon TCs and I believe the higher end Kenko and possibly the Tamorn Pro are recognized by the body. The regular Tamrons are not (I have the cheaper 1.4x Tamron).
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12/05/2006 01:06:06 PM · #9 |
Notice that the notes for the table reference only film bodies. I'm guessing that it's badly outdated. In any case, for modern EOS digital bodies, the behavior is not as is stated there. All focus points are usable up to f/5.6, at least on my 5D, and as I recall that was true on my trusty ol' 10D as well. Can't test that one, it is currently serving another master. |
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