Tele-Convertor / Extender

[V6GTO]

Why would you need to put a 2x converter on smaller lenses? You would use a converter because 300mm or 400mm isn't long enough, not because you want to go 28mm to 56mm. Or am I missing something? Martin.

[murph7355]

You're spot on. The guys added that it shouldn't be much of a problem as you wouldn't ordinarily do it...

[hobo]

Just taken delivery of Kenko Extender this morning and it all seems to be working just as I wanted.

Was a bit worried at first as I had it coupled with a 90-300 Lens & when I tried to auto-focus on an object within say 5 metres it couldn't do it. However, when target is above this distance away I autofocus's with no problem.

Thats for all assistance, as without it I could have ended up spending hundreds & not tens of pounds.

Cheers.

[leszekg]

Just caught this thread a little late. Try www.speedgraphic.co.uk who do Kenko and other teleconverter products. They also offer a no nonsense description of why you can have problems autofocussing with a convertor as follows:

"Customers are sometimes perplexed to find that their converter won ’t autofocus with a particular lens. The reason is an optical one:they lose light -1 stop for the 1.4x,and 2 stops for the 2x.Camera manufacturers design their autofocus sensors to work with lenses of f8 or faster,and so when a 2x converter is attached to a 70-300mm zoom with an aperture range of f4-5.6,this becomes f8-f11,and at the 300mm end,autofocusing stops. It ’s only really a problem however,if you’re photographing moving subjects.”

[srider]

leszekg said:

Just caught this thread a little late. Try www.speedgraphic.co.uk who do Kenko and other teleconverter products. They also offer a no nonsense description of why you can have problems autofocussing with a convertor as follows: "Customers are sometimes perplexed to find that their converter won ’t autofocus with a particular lens. The reason is an optical one:they lose light -1 stop for the 1.4x,and 2 stops for the 2x.Camera manufacturers design their autofocus sensors to work with lenses of f8 or faster,and so when a 2x converter is attached to a 70-300mm zoom with an aperture range of f4-5.6,this becomes f8-f11,and at the 300mm end,autofocusing stops. It ’s only really a problem however,if you’re photographing moving subjects.”

Just a note on the end, for all Canon SLRs except the EOS 3 and 1 series, the limit is f5.6.