# Teleconverter AF modification



## davebmck (Dec 20, 2008)

I have a Canon 1.4 teleconverter under the christmas tree and I have read there is a modification you can make by taping some of the contacts to allow autofocus on lenses with larger minimum apertures than f/4.  Can anyone direct me to information on how to do that?


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## SCguy (Dec 20, 2008)

Quote from Canon 1.4x and 2x extenders

[FONT=Helvetica, Arial, sans-serif]*The Canon Teleconverter Trick*
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[FONT=Helvetica, Arial, sans-serif]*Canon non professional dslr cameras such as the Eos 10d  Eos 20d Eos 30d will cut-off auto focus when they detect a f5.6 lens in addition to a teleconverter.*
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[FONT=Helvetica, Arial, sans-serif]*It's quite simple to get around this by fooling the camera into thinking there is no teleconverter attached and continuing to auto focus by a simple trick.*
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[FONT=Helvetica, Arial, sans-serif]*Just place a thin strip of insulating tape over the three pins on the lefthand side (lens side of the extender). No damage will occur to the camera or teleconverter. Auto focus performance will not be quite as good as f5.6 but when you are using a lens such as a Sigma 500mm f4.5 with a 1.4x teleconverter, the amount of light reduction is minor and auto focus will still be very good.*
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[FONT=Helvetica, Arial, sans-serif]*When you try this on a f5.6 lens such as the Canon 100-400mm L  I.S. USM in combination with a 1.4x teleconvereter, auto focus will generally be poor.*[/FONT]


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## davebmck (Dec 20, 2008)

I wanted this for my 100mm macro, but I sure want to try in on my 100-400mm as well.  Just have to see how it works.


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## table1349 (Dec 20, 2008)

davebmck said:


> I wanted this for my 100mm macro, but I sure want to try in on my 100-400mm as well.  Just have to see how it works.



Keep in mind the Canon 1.4 TC is designed for certain lenses.  Not just from the electrical/focusing standpoint, but from a physical standpoint as well.  The front element of the TC sticks out a bit and with some Canon glass the TC will just not mount.  I believe that may be the case with the 100mm f2.8 macro.  

Here is the compatability chart,

Canon Extender EF 1.4x II Compatibility Chart


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## Joves (Dec 20, 2008)

Hmmm! Makes me wonder if there is a simular work around for Nikkors. Would be nice.


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## davebmck (Dec 21, 2008)

SCguy said:


> Quote from Canon 1.4x and 2x extenders
> 
> [FONT=Helvetica, Arial, sans-serif]*The Canon Teleconverter Trick*
> [/FONT]
> ...


This isn't working for me.  Let me make sure I am doing this right.  Looking at the lens side of the teleconverter and putting the contact pins at the bottom (6 o'clock) there are three pins on the left side that are separate from the other 8 pins.  As I understand it, these are the pins that need to be taped.  When I do this with my 100-400mm it is showing a maximum aperture of f/6.3 and won't autofocus even in bright light.  Do I have the right pins taped?

Unfortunately, the teleconverter won't fit my 100mm macro.  Bummer.  This may have to go back to the store.


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## Garbz (Dec 21, 2008)

Joves said:


> Hmmm! Makes me wonder if there is a simular work around for Nikkors. Would be nice.



Yes buy the Kenko teleconverters without the bs.


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## davebmck (Dec 22, 2008)

OK, for anyone interested it's the three pins opposite the ones I taped described in the post above.  Apparently the directions are for looking at the pins in the 12:00 position, not the 6:00 position as I had assumed.

A picture is worth a thousand words and this link shows one with the tape in the proper location. Taping The Pins on 1.4x tele-extender to restore autofocus in Canon cameras


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## zombii (Feb 1, 2009)

The link in the previous post says this won't work with a 2X converter but I just tried it with a Tamron 2X and my Canon 300mm f/4 on a 5D and it works surprisingly well even in low light as long as there is sufficient contrast. The only problem it had was that it wouldn't work with the focus range set to the 1.5m minimum, it had to be set to the 3m minimum. Small price to pay.


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