1.4x teleplus pro problem

stewsmith

stewsmith

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just attached my 1.4x to a Tokina 10-17 FE and I am having problems with AF. I attached the 1.4x to the lens first and then attached the 1.4x to the body. The body is a 350D Canon. When the shutter is depressed I am getting an an electronic noise which seems to be coming from the lens.

Any help would be greatly appreciated.

Stew
 
Just Googled that and it appears to be an f/3.5 lens. When you attach a 1.4x teleconverter, that is doubled - taking it above the threshold of f/5.6 for autofocus, which is why the camera is not focussing correctly (if at all)?

There is no way to get around it except to manual focus or remove the TC.
 
First of all it is not a good idea to fit a converter onto wide angle lenses.

What is the maximum aperture of the Tokina? If the total with the converter is greater than f5.6 you would lose AF.

Converters are designed for and best used with telephoto lenses!
 
HI thanks for the replies. i understand what is being said here, but i use this lens and camera for underweater use and this combination is widely used for close focus wide angle and wide angle macro photography. i have just checked this on another biody and all is working well. I think perhaops the contacts on the first body may require cleaning. Once again thank you for the speedy replies.

BTW the tokina 10-17 is F3.5-4.5
 
What body did you check it on that it worked?

Canon says that a lens with a maximum aperture of (I think this is right) less than f/5.6 (so, higher f/ number) will not autofocus except on the 1 series bodies. 1 series bodies will autofocus up to and including an f/8 lens.

This problem you are experiencing is a limitation of the device, not a fault! :)
 
just checked it on another 350d and 5d mk2 and it they both AF ok

Stew
 
trencheel303 said:
Just Googled that and it appears to be an f/3.5 lens. When you attach a 1.4x teleconverter, that is doubled - taking it above the threshold of f/5.6 for autofocus, which is why the camera is not focussing correctly (if at all)?

There is no way to get around it except to manual focus or remove the TC.
Click to expand...

Its only a stop for a 1.4X converter so it should still be OK
 
Dogfish_magnet said:
Its only a stop for a 1.4X converter so it should still be OK
Click to expand...

Perhaps I am getting confused here - but my thinking is that with the f/stops of this lens the teleconverter is still going to take it above the maximum focuss-able aperture on rebel bodies.

Why then, it's working on another 350D is beyond me.

EDIT: Ignore me, I did my math wrong as usual.
 
Just a thought... did you test the lens at the same focal length on both bodies?

If it's f/3.5 max at 10mm, +1 stop will take it to f/5.0 and AF should work.

At 17mm, it'll be f/4.5 + 1 stop = f/6.3, beyond the f/5.6 limit.
 
I cleaned the contatcs and all is working fine now. Even at 17mm AF still works.

Stew
 
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