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11/24/2006 01:52:07 PM · #1 |
So I'm looking into new gear. Is it true that the 350D won't autofocus below F/5.6? I was thinking about getting the 70-200 2.8 with a 2x Extender. So I'd end up with precisely F/5.6. Does that mean that the camera will have a hard time focusing, or will this not work at all, or is it just fine? (Yes yes, get a new camera etc... later, maybe.)
I was also wondering whether extenders merely reduce light or whether they effectively change the aperture and hence the DOF?
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11/24/2006 01:59:56 PM · #2 |
In bright light, where you'd typically use a "400mm" lens at f/5.6 it should work fine. It is not gonna be a happy camper in lowlight though.
Just something to consider.
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11/24/2006 02:11:07 PM · #3 |
Yes, the aperture becomes f/5.6 and yes, the DOF changes as well. For example, 200mm at f/2.8 focusing on a subject 20 feet away, you'll get 6 inches in focus (approx 3 inches in front of and behind the subject, but that's not the full story). If you put a 2x extender on the lens, you'll get f/5.6 and 400mm. Focusing on the same subject 20 feet away, you now have approximately 3 inches total focus.
And yes, f/5.6 is still usable with auto focus. If you were to put the 2x extender on an f/4 lens, you would lose auto focus.
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11/24/2006 02:24:22 PM · #4 |
If you are, indeed, going to use a 2x TC with the 70-200, I would like to suggest that the IS version would perhaps be best, if you are going to use the combination hand-held. A lot more expensive, I know, but at that focal length, one needs all the assistance one can get.
Another thing is that, from my experience, if you use the 2x TC, you need to stop down to f/8 or preferably f/10 to get more sharpness. Even to my eyes, the softness at f/5.6 is apparent with the 2x TC.
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11/24/2006 03:30:31 PM · #5 |
Thanks for the insights so far. dwterry, would the DOF in that case be the same as on a genuine 400/5.6 lens?
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11/24/2006 03:36:46 PM · #6 |
Originally posted by gloda:
...would the DOF in that case be the same as on a genuine 400/5.6 lens? |
Yes, the combined lens+converter is in every way a 400/5.6 lens. Be aware that the 70-200/2.8 + 2.0x converter combination is only marginally useful. You really will need to stop it down, probably two stops, to get the same sharpness as wide open without the converter. So you'll be at f/11, or at best f/8 with this combination. |
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11/24/2006 05:18:50 PM · #7 |
Thanks. Not very useful then. I was basically looking for a sports photogrphay solution which would allow me to occasionally go beyond the 200mm for zoo shots and the like.
I assume that similar issues will arise with the 1.4x? Or is sharpness not that much an issue with that extension?
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11/25/2006 07:52:37 AM · #8 |
In my limited experience, the 1.4TC does nowhwere near as much harm to the image quality as the 2x does.
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11/25/2006 08:10:04 PM · #9 |
Originally posted by gloda:
Thanks. Not very useful then. I was basically looking for a sports photogrphay solution which would allow me to occasionally go beyond the 200mm for zoo shots and the like. |
I use the 2x extender with my 70-200 and leave it at f/5.6 most of the time. Chances are pretty good that nearly all of the shots in this folder are Canon 70-200 2.8L IS plux 2x extender at f/5.6.
So while I agree that the lens gets a little soft with the extender on it, I still use it quite effectively in shooting soccer.
Message edited by author 2006-11-25 20:10:21.
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