TC Auto focus
 

Hello all,

Im currently a Canon user and ive been toying with the idea of moving across to Nikon. But i have a question
If i got say, the Nikon 70-200 Af-s VR and a 2x converter, will it still autofocus? Because if you put a 2x converter on a Canon lens it wont.

Thank you in advance

Dean

The Nikon 70-200 is an f2.8 lens so will work fine with a 2x (effectively becoming a 140-400 f5.6), the AF will be slower than without the 2x but will still be acurate. Canon make four different 70-200 lenses (f4, f4 IS, f2.8 and f2.8 IS), either of the f2.8 lenses will retain AF with a 2x but the f4 lenses with only AF with a 2x if used on a 1D.

Yes you can stay Canon (you naughty boy even thinking of Nikon! :eek:) have your 2x converter and retain your auto focus.

I do not understand this Dean, Like Peter and Mike have said you can get AF with a 2x on a Canon, its just a case of having the right lens or Camera.

maybe my problem is that im not using a 1D! I use two 30D's and none of them allow me use autofocus. I use a sigma 70-200 f2.8 and a 300mm f.4L and none of these allow the autofocus to work on the 30Ds
I was just wondering if the same problem occured with the Nikon D300?
If it doesnt im tempted to look at a D300 with a 70-200 and use a 2x tc with it and keep my canon 30D with the 300mm.
Im a motorsport photographer and think that the 70-200 with a 2x on would make a great backup/main camera

I have no experience of Sigma lenses but the 70-200/2.8 should AF OK with a 2x tc on any Canon body (inc 30D) as this only takes you up to f5.6 - AF would inevitable be slower with a 2x (as it will on any Camera/lens combo) but it is very strange if it does not AF at all. Could it be that there is a problem with the converter?
The 300/4 will not AF as it takes you up to f8.

FWIW I regularly use a f2.8 lens with 2x tc and AF is fine on both the 7D and 40D (it was also OK on my 30D before I sold it).

The 30D will only AF if the max aperture of the lens (or lens and tc combo) is f5.6 or wider, a 1.4x tc will cost you one stop while a 2x will cost 2 stops. So your 300 f4 used with a 1.4x will become a 420 f5.6 and still AF fine and with a 2x it becomes a 600 f8 so you'll lose AF. The Sigma 70-200 being and f2.8 should AF fine with either a 1.4x or 2x tc (becoming 98-280 f4 with the 1.4x and a 140-400 f5.6 with a 2x).

I had a Sigma 70-200 f2.8 for a while and did use it with a 2x tc (I think on a 350D or 400D at the time) it retained AF however there was noticable slowing in AF speed so it wouldn't be ideal for motorsport. What brand of TC have you tried on your lenses, I wonder if this is causing the problems?

Thank you for your time guys, i appreciate it.
Im using sigma convertors i have both a 1.4 and the 2x
The sigma 1.4x works a treat on my 300mm and its my work horse setup! 95% of my stuff is taken using that setup. But when i put the 2x on it just wont autofocus at all, i was told that Nikon users dont have this problem.
just re reading this through and im starting to wonder why i need a 2x on the 70-200?? it gives me the same 400mm as im getting with the 300+1.4!!
maybe i should just get a second hand 1D instead!!!

Still does not explain why the 2x does not work on your 70-200/f2.8 Dean.

BTW I would have thought that for fast moving action like motor sport, using a 2x tc with any Camera/lens combo would mean that the AF would be too slow (and that includes Nikon).

Even if you got a 1D and used the 300/4 + 2x tc I suspect the AF would be too slow for your needs (also IQ would take a big hit).

Im not sure why it wont auto focus, ive got to send it off to be fixed as the focus ring has locked solid on it now so it wont focus at all, so maybe when it comes back it will work?!
As regards to 2x, i dont have any knowledge of them because as like i say ive never managed to get one to work, but if it will slow AF down that much i dont think i'll bother