latest firmware for 5d iii

[bmpress]

The latest firmware states that focus can be obtained at f8, so I assume that my 100-400 will work with a 2X extender. My question is whether it is possible to autofocus with a Tamron 1X or 2X unit?

[Bob Atkins]

Assuming the AF at f8 works, the 100-400 would work with a 1.4x but not a 2x. The 100-400 is f4.5-5.6. With a 2x that would become f9-f11.

It should AF OK with a Tamron 1.4x, but again, with a 2x you may run into problems.

I'd advise buying your TC from a store like B&H, Adorama or Amazon (see links below) which have a "no hassles" return policy so if things don't work as you expect, you can return it!

[bmpress]

Thanks, Bob. In the back of my mind there was something written about taping certain pins to get the teleconverter to work. Can you please talk about that.

Barry

[Bob Atkins]

You can tape pins which prevents the camera from recognizing the TC. Most EOS bodies disable AF when a lens slower than f5.6 is detected because the AF sensors don't work well at f8. So with the pins taped and the TC information to the camera lost, it still thinks the lens is, say, f5.6 when it's actually working at a maximum aperture of f8. Sometimes, under some conditions, it will AF OK, but you are really pushing the limits of the AF sensors and the camera won't correctly adjust AF speed for best AF.

A camera that doesn't disable AF at f8, like the 5D3 and 1D X with the latest firmware doesn't need the pins taped to work at f8. Presumably the AF sensor in those cameras (but only the center sensor) can work at f8, but probably only just. If you're thinking of fooling it into working at f11 by pin taping, my guess is that you'll be disappointed. It's very unlikely the AF sensors will operate well (if at all) at f11.