A question on tele converters

J

jason90

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I purchased a 2x Kenco TC today, I was under the impression that using a TC that you loose F stops

I tried it in the shop on my 400D & Sigma 70-200 2.8 and was suprised I was still getting 2.8

Is this correct or is it just fooling the camera, have nt been able to take any shots yet but will do later
 
IT is fooling the camera. It doesn't matter as the camera meters through the lens anyway. The way to prove this is to look at the same scene with and without teleconverter. With the converter, the shutter should open for 4 times longer than without.

Some of the converters don't report so that the camera will try to AF on a less with less than f/2.8 aperture when fitted on a 2x. Normally, with less than f/5.6, a 400D won't even attempt to AF.
 
which one did you get the pro 300 ? I did a test the other week and on the x1.4 I lost around 1 stop that was with a 5D and a 70-200 2.8
 
Simplisticly. You deffo wont get 2.8 on a 2.8 lens with a TC .. thats written in stone for any combination so if you see it then you know theres somehting amiss :)
 
Thanks for the quick replies as usual

AF still works, allbeit slightly slower, but the test will be actually using it I guess

Model is a Teleplus MC7 DG
 
Yes, Canon and Sigma both report as teleconverters so you will see the drop. Some of the Kenkos don't.

Canons apart from the 1D will AF down to f/5.6 so if your teleconverter reports, you need an f/4 lens for a 1.4 times and an f/2.8 lens for a 2x. The 1D will AF at f/8 (although not as well) so I can use a 2x on my 500 and get 1000mm f/8.

If a teleconverter doesn't report its presence then the camera will still try to AF and may, or may not, be successful.
 
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