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Old Sep 2, 2006, 10:51 AM   #1
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Please explain teleconverters. How they work. Different situations, etc.

Assume from "tele" they may help extend the reach of a particular lens. Please explain with any relevant examples.

Thanks!
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Old Sep 3, 2006, 1:54 PM   #2
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I read lots about these before I bought mine. Many people said don't buy the 2x extender because the reduction in image quality compared to the 1.4x.

I ignored this and bought the 2x anyway thinking that the 1.4x is hardly worth having since it's not much extra reach.

My 2x extender sits in it's little pouch never used. I wished I'd believed the comments on quality.

My 70-200mm f/2.8 IS is great on its own but with the extender it's blah.
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Old Sep 3, 2006, 4:10 PM   #3
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I bought the x1.4

Use it with my 70-200 L 2.8 USM

I find its a balancing act..

I prefer really crisp images, but the extra distance that can be brought into th frame and fill 3/4's of it, is significant...

Also, I was surprised by theamount of light lost in moving from f2.8 to f4... probably costs me about 400s in shutter speed, which on a cloudy day and fast moving action, is a real pain...

I'd say to be honest, if you've got a decent L in the 70-200 range, the 1.4 is a no-brainer, unless you're going for a 300 or 400mm zoom.

Finally, sorry no physics here, I've got a rough idea of whats involved, but from a simple end-user point of view, I thought i'd give my feedback.


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Old Sep 3, 2006, 6:11 PM   #4
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well there are good teleconverters and bad teleconverters just like anything else. I have both a 1.4x and 2x Sigma TCs that I use with my Sigma 70-200 f/2.8 with almost no quality loss even when both are stacked together. But they are just like anything else, if you have really good quality "L" glass and stick a cheap filter over that great glass your photos will suffer from the weakest link. Buy quality glass and a quality Teleconverter and you should be fine with either the 1.4x or the 2x.
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Old Sep 3, 2006, 10:35 PM   #5
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Caboose wrote:
Quote:
well there are good teleconverters and bad teleconverters just like anything else. I have both a 1.4x and 2x Sigma TCs that I use with my Sigma 70-200 f/2.8 with almost no quality loss even when both are stacked together. But they are just like anything else, if you have really good quality "L" glass and stick a cheap filter over that great glass your photos will suffer from the weakest link. Buy quality glass and a quality Teleconverter and you should be fine with either the 1.4x or the 2x.
I agree with Caboose
Check over here:
http://www.photozone.de/8Reviews/len...0_28/index.htm
http://www.photozone.de/8Reviews/len...28is/index.htm

-> at least at the center, the measured MTF @ 200 and 280(with the 1.4x) are quite similar, only the peripherals fall off a little bit but... if you notice @ f/4 with the 1.4x on the lenses are actually sharper at the center wide open on both lenses than @ f/2.8 (without the TC)! :?
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Old Sep 28, 2006, 7:16 AM   #6
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I will try to just provide the basic facts of a TC, final decision wheather & when to use themmust be left to you.

A 1.4X TC will cost you 1 f stop & a veryslight degradation in quality. Latter depends on the TC brand. A 2X TC will cost you 2 f stops & a bigger degradation in quality. The amnount of degradation depends on what you do with the final picture (eg make a 12x16 print or just a PC slide show).There are also some TC's (Canon comes to mind) that will not work with some lenses. Above a certain f stop (camera dependent) the AF (auto focus) feature will start to hunt or cease altogether because of light loss).

Trust this will help.
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Old Sep 28, 2006, 9:13 PM   #7
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I see no loss when using mine with my 300 2.8 IS and its tack sharp wide open. I have not tried a 2x yet but plan on doing so. You can see from the sample below the gain is not that great.


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Old Sep 29, 2006, 5:55 AM   #8
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Widowmaker wrote:
Quote:
I have not tried a 2x yet but plan on doing so.
FYI - Photozone already neasured it for you (MTF's @ 600 with TC vs 300):
http://www.photozone.de/8Reviews/len...28is/index.htm

-> With a 1.4x it's a hard to tell wide open, like on the 70-200 f/2.8 links I posted before, the IS version resoved better wide open with a 1.4x TC than the same lens without - At least at the center the MTF measured are: 1678 @ 280mm f/4 vs 1599 @ 200mm f/2.8
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Old Sep 29, 2006, 10:04 AM   #9
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You asked for examples. I use a Sigma 2X on my 70-200 for zoo shoots when I wish to hand hold. It is much easier to hand hold than my other lens options, so any loss to quality is a tradeoff for the burden of the tripod. I could buy a Canon 400 L f5.6 but I don't wish to duplicate a focal length I have covered with my current lens assortment.


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Old Sep 29, 2006, 10:45 AM   #10
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Kind of off topic... But I really like the picture... Great shot....IMHO........ I like the expression on the lions/tiger face..........

R~
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