Extenders/Tele Converters

greedy123 · 2 Jul 2009 at 13:04

So I'm wanting an extender/Tele Converter for use with both my Canon 70-200mm f/4L and Sigma 150mm macro. I'm wanting a 1.4x one ideally (so I can keep auto-focus) but I am not sure which to get. Apparently the Canon one, which is what I was favouring, only works with Canon lenses and won't work with my sigma.

Does anyone know if this is true and if there is a extender which will work with both lenses? :confused:

neil_g · 2 Jul 2009 at 15:09

i think the canon tc protrudes further into the rear element which causes issues on some lenses.

Gnomey · 2 Jul 2009 at 15:43

The Kenko teleconverters have greater compatibility than the Canon ones. The Pro 300 1.4x is meant to be almost as good as the Canon 1.4x. This fits both the 150mm and the 70-200mm. It is also quite a bit cheaper than the Canon one.

greedy123 · 2 Jul 2009 at 19:06

Ok sounds like its decided then! Will I the lenses keep auto-focus with the kenco? Also what happens with exif? Does the camera still know what lens is attached etc?

Gnomey · 2 Jul 2009 at 20:52

The teleconverter will report that it is attached, so 150mm will show as 210mm. You will still have AF with both lenses but there will be some loss of focus speed.

greedy123 · 2 Jul 2009 at 21:05

Ok great. I'm watching one on the bay right now. So much cheaper than the canon one!

greedy123 · 16 Jul 2009 at 09:36

Bought the sigma 1.4x in the end. Works with both the sigma lens (obviously) and the canon 70-200 f4 IS!

Really pleased with it so far! Weridly it seems to work better with the canon than the sigma. The sigma macro loses auto focus at short distances oddly, works fine otherwise but as you can imagine its the short distances which are important on a macro lens!

The exif data remains intact with the teleconverter and it correctly displays the reduces f-stop on the camera during shooting and correctly multiplies the focal length.

There is a noticable loss of sharpness when used with the sigma 150mm macro at closest focus possible but only when viewed at full crop. More testing is needed however as I only had a play with it for 10 minutes.

neil_g · 16 Jul 2009 at 10:50

id hazard a guess that your minimum focus distance is affected by the t/c

greedy123 · 16 Jul 2009 at 11:36

Well I can manual focus to the same minimum focus distance just the auto focus stops working about 5cm before than for some reason, oh well... manual focus is preferable for macro anyway.