[malgos]

Have just taken delivery of a 300d together with a 100-400f4.5-5.6 IS USM lens and EF 1.4 Extender. The camera works fine but when the extender is attached to the lens it won,t auto focus. The camera shop have tried two camera bodies and two extenders and still can,t get autofocus to operate. I have spoken to the Cannon helpline who say the lens and extender are compatible and are going to look into the problem and get back to me in the next couple of days. Cannons web site says that the lens and extender are compatible so should autofocus still work with the extender fitted? Anyone else got a similiar set up and if so does autofocus work with the extender? Any help or suggestions appreciated. This equipment did,nt come cheap and I only bought the extender because I was assured it would Autofocus with this lens.
HELP!
Malcolm

[yellow_belly]

Hi - from memory the autofocus will only work with lens that have a max aperature larger than F5.6, not sure if this is with or without the extender but as you are having problems it is probably with the extender and as you lose 1 stop with a 1.4 extender it brings your lens outside the limits - sorry.

Terry

[Steve G]

Hi Malgos,
What Terry says above is sadly very true. The camera is programmed for autofocus not to work when the maximum lens aperture (or lens + convertor effective aperture) is smaller than 5.6. Apparently this is because the lower light levels below f5.6 may prevent proper autofocus function. The same will apply if you used an f4 500mm lens & 2x convertor (> effective f8 aperture) though autofocus will work using an f4 lens + 1.4x convertor (effective aperture of f5.6).
It's a real bu@@ar!!

[malgos]

Thanks yellow belly and Steve G.At least I know its not supposed to work I,ve just been given duff information when I ordered. I,ll just have to use manual focus when the extender is attached.
I knew some one on this forum would have the answer.
Malcolm

[Paul Rule]

Sounds like your camera dealers have not got a clue . They should have known that and advised accordingly. I have just got a second user 1.4 to use with my 400f5.6L, which will take me back to basics, although if you tape over the 3 righthand pins (lens side) of the adaptor, auto focus will work (although probably only on nice sunny days) I have yet to try this myself.

Paul

[peteh]

Hi
Ive tried that pin taping trick and even though I thought it was going to goof up my lens,
it worked perfectly and was unbelieveably easy to do.
I have used my 100-400 with 1.4tc to af even on birds in flight too!
The only downside I have found is that if you take any notice of your exif data, then the focal length comes out at 400mm rather than 560mm. But that is not exactly a major disaster.
regards
Pete.

[malgos]

Thanks guys I,ll try that.
Malcolm

[Steve G]

Originally Posted by peteh

Hi
Ive tried that pin taping trick and even though I thought it was going to goof up my lens,
it worked perfectly and was unbelieveably easy to do.
I have used my 100-400 with 1.4tc to af even on birds in flight too!
The only downside I have found is that if you take any notice of your exif data, then the focal length comes out at 400mm rather than 560mm. But that is not exactly a major disaster.
regards
Pete.

Having sold my children into slavery I got a Canon 1Ds. It seems not to be restricted by the loss of autofocus using a f4 500 lens + 2x convertor (> f8 effective) but autofocus operates with the centre sensor area only. If you push the boat out on a bright day & use the 500 lens + 1.4x & 2x convertors it will still autofocus ( though less rapidly) but the exif data records this combo as a 1000mm effective lens (instead of 1400) despite the camera monitoring 3 stops of light reduction from f4. Images using this combo are slightly soft but very useable & once sharpened in photoshop are quite good. This combo yields 28x magnification with a Tiff file of 32mb allowing marked "digital" enlargement in-computer- which approaches digiscoping magnifications but the new Canon 1D mkII looks like it'll be even better for our type of photography ....at half the price!