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Old Jun 14, 2006, 12:40 AM   #1
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Am trying to decide between these two lenses to use on a 30D. If reach wasn't an issue, of course I would go for the faster 70-200, which by all accounts is a great lens. However, probably the majority of the time I will be shooting surfing at 400mm. I figure the 70-200 + 2x converter will give me a maximum aperture and reach as the 400. What disadvantages would there be in using the 70-200 + 2x tcon combination over the 100-400. I've heard that I will lose autofocus ability, image sharpness/quality etc. Is this true? Anything else to consider?



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Old Jun 14, 2006, 7:38 AM   #2
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The 70-200 2.8 will still maintain autofocus with a 2X tc since the aperture will only be reduced to 5.6. So that's not an issue. But it will focus more slowly and be softer than the image from the 100-400. If you believe you'll be at 400mm the majority of the time you use the lens then the 100-400 wins hands-down.

That being said - there is the age-old (and some say myth) debate about the push-pull of the 100-400 being a 'dust vaccum'. Now, I've never noticed a problem with my 100-400 in that regard but if I were shooting on a beach constantly I would be more concnered with it. It doesn't have to be a vaccum - I would surmise just having sand on the lens when it's extended and then you retract - it's going to pull the sand inside. Have you considered going with a prime - something like the 400mm 5.6? I just hesitate to ever recommend a solution where you know you'll be using a 2x TC all the time as long as there are other alternatives (obviously when you get to over 400mm your alternatives shrink dramatically).
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Old Jun 14, 2006, 5:09 PM   #3
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Thanks John. Thought that might be the case. Will probably go with the 100-400 because I will use the 400 end more often, and don't like the sound of slower focus and softer images. Besides, the 100-400 is quite a bit cheaper than the 70-200 and a tcon.

Have also read quite a bit about the 'dust vacuum' issue of the 100-400. I'm probably going to buy or make a rain/dust shield to use on it when shooting around sand. It is quite a concern though. Thought about the 400 f5.6 prime, but really want the flexibility of the zoom.

Thanks again!
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Old Jun 16, 2006, 10:55 PM   #4
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Chris, you'll really want to read this artice:


Also, I have the 100-400L, and I use it to shoot at the beach all the time. Dust is a non-issue with this lens. I'm not saying it doesn't get a little dust in it, it does. But this dust cannot be seen in the images it produces. If you don't believe me, try this: Tear a tiny corner off a piece of paper. Wet the piece, and stick it on the front of a lens. Now look through the lens (attached to a camera, of course). You probably won't even be able to see the paper!The point is, dust on or in a lens is practically irrelavent.

Hope this helps.

Chris M

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Old Jun 17, 2006, 6:36 AM   #5
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Dust on the lens was never an issue... But dust on the sensor is and always will be
-> On film one has a new frame everytime the shutter is released, but on the digital the same stationary sensor is 're-used' for every shot...

I have the 100-400L too, but the potential is always there over lenses (with internal zoming) that do not extend or retract.
(All anyone has to do is to take the rear lens cap off and feel with your hand all the air behind this lens when its being pumped)
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