Another Kenko Teleconverter Q

[JanHarper]

I am being a bit thick today. When the instructions say, "AF function may not work properly if the integral aperture of the lens used with Kenko TELEPLUS DGX is more than F5.6." Does that mean it has to be manually focused at F8, F11, F.16 etc? Thanks.

[Stan]

Re: Another Kenko Teleconverter Q

most canon crop sensor cameras will only autofocus with lenses that have a maximum aperture of f 5.6. If you add a 1.4 converter or whatever make, you lose a stop of light so if your lens is a f5.6, it becomes a f8 and you can only focus manually. If your lens is an f4 or f2.8 then adding a stop of light will still bring both within the maximum f5.6 and therefor you will be able to autofocus

Stan

[El Sid]

Re: Another Kenko Teleconverter Q

Depending on the camera and lens/converter combo you may find AF at an effective f8 is possible - I have an old MC7 which does allow the lens to AF beyond an effective f8 aperture though that seems to be the limit, anything smaller tries but never locks... In reasonable light with a fairly contrasty subject it seems accurate too.

I also have a Pro-300 which turns AF off when attached to my 70-200 L but does allow AF with an ancient 70-210 F4 I have...

On the whole I'd say assume that AF is not possible at an effective F8 and if it does that's a bonus - anything else is strictly manual - and tricky...