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Old Apr 4, 2005, 4:32 PM   #1
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Can someone please tell me whether i can use a 1.4 or 2x tele conv lense with a 135-400mm on a canon 20D?
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Old Apr 4, 2005, 6:08 PM   #2
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That Canon has a conversion factor or 1.6X, which would give you a top zoom of about 640 MM without the teleconverter. That's over 18X. Are you photographing dangerous carnivores?

You need to check the threading on the canon or your lens and your teleconverter to see if you can attach it without step up or step down rings. It would be easier for people to give you useful advice if you let us know the details about your lens and the teleconverter. What company? What model?
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Old Apr 4, 2005, 6:22 PM   #3
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The 1.4X converter is only one stop slower so it would be preferred since it will allow higher shutter speeds than the 2X.

robbo wrote

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You need to check the threading on the canon or your lens and your teleconverter to see if you can attach it without step up or step down rings. It would be easier for people to give you useful advice if you let us know the details about your lens and the teleconverter. What company? What model?
DSLRs use teleconverters that mount between the lens and body, not thetype which mount on the front of the lens like digicams use.

Ira

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Old Apr 5, 2005, 2:58 AM   #4
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Thanks for reply the lense is a Sigma 135-400mm F4.5.6APO and yes you are probably right about the carnivores!! but i do mostly wildlife and i do mean wildlife not the odd sparrow, but i have only recently moved up to SLR's and the lense game is a big learning curve, i have been using the 75-300 4.5-6 (SIGMA) but was told cannot use tele conv with this as it will slow things down too much.
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Old Apr 5, 2005, 6:57 AM   #5
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i have been using the 75-300 4.5-6 (SIGMA) but was told cannot use tele conv with this as it will slow things down too much.
Something to keep in mind - the 20d cannot auto-focus with apertures slower than 5.6. So, when you use a teleconverter on a 5.6 lense you will lose autofocus. I would check in the Canon lense forum - there are some serious wildlife photographers that can give you some good advice there.
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Old Apr 5, 2005, 10:56 AM   #6
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I would check on Sigma's web site to see if their TC will work on that lens. The odds are that it won't, but it might.

JohnG is right about the loss of AutoFocus with a teleconverter. And the view finder will be darker, so it will be harder to manually focus.

If you area really serious about wildlife photography, the only solution is real money. The Canon 300mm f4 + TC works well. Its a cheap way to get a 420mm f5.6 lens that is still quite sharp. The 100-400L f4.5-f5.6is a good lens (but slightly more expensive than the previous combination, I believe) but you can't put a TC on it without loosing AF.

Sigma's 100-300 f2.8 is good from what I've read here, but I don't know anyone who personally has it. That you can put a 2xTC and still AF (600 f5.6) but I don't know how good it is optically with the TC. If you're shoting wildlife you have the problem of stoping the action. Loosing 1/2 your shutter speed (the difference between f4 & f5.6) can cost you the picture. But that difference can mean a lot more money. Canon's 400 f4 is (unfortunately) DO, which means light and really expensive (over $5K USD, so too high I bet.) Ideally you'd like a 400 f4 at a reasonable price so that could take a TC when you needed it and still AF.

Oh, don't forget the Sigma 50-500. I've heard about (and seen) really good stuff produced with this lens. It won't get a TC without loosing AF 'cause it's f6.3 at 500mm. But it had decent reach.

Eric
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Old Apr 5, 2005, 4:09 PM   #7
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Thanks for that have really learnt something here, and will do as you advise and look on canon lense forum. regards.
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Old Apr 5, 2005, 4:14 PM   #8
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Thanks for all your advise, really helpful. Did,nt know about the loss of shutter speed, shows how much i have got to learn. I have had to make do with the lense i am speaking about (135-400mm F4.5-5.6) because of exactly what you said "The prices" i managed to get this second hand (in excellent condition) but i can only dream on at the moment about a faster lense!. regards. Bev.
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Old Apr 5, 2005, 4:14 PM   #9
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Thanks for all your advise, really helpful. Did,nt know about the loss of shutter speed, shows how much i have got to learn. I have had to make do with the lense i am speaking about (135-400mm F4.5-5.6) because of exactly what you said "The prices" i managed to get this second hand (in excellent condition) but i can only dream on at the moment about a faster lense!. regards. Bev.
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