Silver lens, yes or no?

[Bengeo]

The 70-400mm SSM is definitely compatible with the converters but only the 1.4X offers AF.

The manual states that both converters are MF only. The 1.4x will be at F8 at the long end and so shouldn't AF?

Andy

[David Kilpatrick]

Hopefully the 1.4X may work. I don't think anyone has tried it. I have often got converters to work at f8 when they should not, in the past, but some do lock out AF through their programming. I was able to AF with my first 70-210mm f4 and a 2X Teleplus 7-element (I no longer have that), despite it being f8, and that was on very early AF bodies - probably the 7000 and 9000.

David

[PhotoTraveler]

It won't AF because Minolta-Sony AF system is only good to F6.3 or 6.7. The 500RF autofocus while F8 do to special optical reasons due to being a reflex. Normal lenses cannot AF at F8 on minolta.

This limit is pushed by the 4.5/400 which can just get in AF with the 1.4x TC because it becomes a F6.3. But put the 2x on it, and you are over and out of AF. Put the 2x on the 4/300, and it won't AF either, as it is F8, and not the reflex.

The reason some people get some stuff to AF is the use of 3rd party TCs which do not report correctly. They camera still thinks you are a F4 or F5.6 even with the TC on. The sensors go for it and it works. You are just outside of the spec range, but the system goes for it because it doesn't know it's past the governed limit of F8.

If you could find a 3rd party TC that supports SSM (probably only needs to be 8pin) but doesn't report the Fstop change correctly, you could hack that rom into the minolta TCs and make it work. Maybe someday if I ever have such a lens, I might get bored, take a kenko extension tube with 8 pin contacts hack the contacts into the TC with through wires. You know could have the Minolta-Sony APO TCs and put it on a lens like the 70-400 and it would probably work in AF.