Urgent Advice Required.

[otooleg]

Help! I currently own a Sigma 170-500mm 1:5-6.3 telephoto lens but intended to buy a 100-400 IS L Canon lens on the understanding that I could use a 2x converter with is making it 200-800.

I now understand that Autofocus doesn't work with the 2x converter therefore making my purchase questionable. I am obviously aware that the real plus of purchasing the lens is that it has Image Stabilisation and in theory the quality should also be better - but the problem I have been having with the 170-500 even with a Canon D10 giving it 1.6x mutiplication, is that I never seem to be near enogh to what I like to photograph - wildlife. Hence the wish for 800+ focal length. For your information - no I cannot afford a longer fixed focal length.

Comments please.

Regards

George

[Stemmy]

Yes

100-400 L IS f4-5.6 with converter, Manual focus unless used on an eos 3 or 1v, or 1dMkII, or 1ds

This is as much as I can find out.

Worth giving canon a bell to clarify.

[england1965]

http://www.warehouseexpress.com/photo/lenses/canonlens.html?cd=20061013

There is a list of lenses here that are compatible with the x2 converter

I'd double check with Canon though because it used to say "only this list of specific models".

It's been a while - but I used a Jessops x2 converter on my 100-400 and had no problems with Auto-focus (on a 1ds mind)

Cheers

Mark

[DennisB]

I think the thing that determines whether a lens and converter will autofocus is the f number of the combined optics. My own cameras, Fuji S2 and S3, will autofocus with my f2.8 lens and 2x converter, but not with my f4.5/f5.6 lens and 2x converter. I would imagine that specific cameras their own requirement of minimal amount of light needed to autofocus. Perhaps it is in the manual somewhere for the Canon cameras.