[Steve400]

Hi, i just want to clarify a couple of things.

i have the canon 70-200 f4 L and am contemplating getting a converter for it. would i be right in saying that the AF will work ok with the 1.4x converter raising the fstop 1 notch but the AF will not work with the 2x converter??

thanks in advance,
Steve

(sorry this should probably have been in the lenses section)

[gsgary]

Originally Posted by Steve400

Hi, i just want to clarify a couple of things.

i have the canon 70-200 f4 L and am contemplating getting a converter for it. would i be right in saying that the AF will work ok with the 1.4x converter raising the fstop 1 notch but the AF will not work with the 2x converter??

thanks in advance,
Steve

(sorry this should probably have been in the lenses section)

That correct i have that lens and have used my1.4x with it and its good if you want examples let me know, but not tried my 2x zooms don't work too good with the 2x

[Markulous]

Fairly certain that, as a generalisation, it's the 2 stops that the converter loses on the 2x that makes AF difficult. Most lenses will cope with 1 stop loss - as found with 1.4x

{BTW, moved the thread. altho fine where it was, TBH )

[Steve400]

ah thats fine, thanks.

i would probably need the 1.4x converter then! i likely wouldnt really need the 2x anyway!

Thanks!

[Steve]

When you connect a 1.4X converter to the 70-200F4L lens it makes it a F5.6 lens. It does not affect AF at all. When you connect a 2X converter to the same lens it makes it a F8 and again it doesn't not affect AF at all...HOWEVER what it does do (depending on the camera body) is communicate this information and in the case of a 2X converter and F8 the CAMERA will switch of AF if its not a 1 series (read pro body). The reason for this is that as you add in longer converters it reduces the amount of light that reaches the sensor and the auto focus system in the camera and for the standard bodies Canon (and Nikon as well as far as I know) regard this as taking it out of their specifications for effective AF. With the pro series of bodies they have a much better AF system which is far more sensitive and can function in much less light...hense why they work fine at F8.

So the simple answer is that when using TC's at F5.6 the Af will work fine on all bodies but when using a TC at F8 or above it won't unless you have a pro body. Incidentally if you are shooting in good light and wish to use a 2X with AF on a non pro body, there is a little trick that involves placing tape across two of the contacts on the TC, this fools the camera body and allows AF to attempt to work. Your results will be very dependant on the amount of light though...its worked for me in the past but as usual here you are taking the equipment outside of its specified working range and your mileage will vary.

HTH

[gsgary]

Originally Posted by Steve

When you connect a 1.4X converter to the 70-200F4L lens it makes it a F5.6 lens. It does not affect AF at all. When you connect a 2X converter to the same lens it makes it a F8 and again it doesn't not affect AF at all...HOWEVER what it does do (depending on the camera body) is communicate this information and in the case of a 2X converter and F8 the CAMERA will switch of AF if its not a 1 series (read pro body). The reason for this is that as you add in longer converters it reduces the amount of light that reaches the sensor and the auto focus system in the camera and for the standard bodies Canon (and Nikon as well as far as I know) regard this as taking it out of their specifications for effective AF. With the pro series of bodies they have a much better AF system which is far more sensitive and can function in much less light...hense why they work fine at F8.

So the simple answer is that when using TC's at F5.6 the Af will work fine on all bodies but when using a TC at F8 or above it won't unless you have a pro body. Incidentally if you are shooting in good light and wish to use a 2X with AF on a non pro body, there is a little trick that involves placing tape across two of the contacts on the TC, this fools the camera body and allows AF to attempt to work. Your results will be very dependant on the amount of light though...its worked for me in the past but as usual here you are taking the equipment outside of its specified working range and your mileage will vary.

HTH

And it can burn your camera

[Steve]

Originally Posted by gsgary

And it can burn your camera

I don't understand that comment at all...perhaps you would like to clarify

[gsgary]

Originally Posted by Steve

I don't understand that comment at all...perhaps you would like to clarify

By taping the contacts to make it AF at F8 can damage the auto focus if you don't have a pro body quite a few reports of it on other sites