Originally posted by SOldBear Unless a tube also supports AF, six contacts is better than seven.
Why? I don't remember. I'll have to dig up my notes and report back.
The test is with a K-7 body and these two tubes:
Both tubes have anodized (black) on the surface mating with the camera. On the 6-pin tube, at pin 7 position, the surface has been sanded to bare metal.
The 6-pin tube (right, actually a gutted 2X TC) works fine with any lens. Of course there's no AF.
The 7-pin tube has these problems:
- With SDM lenses (DA* 16-50 and DA* 50-135), focus confirmation and focus-trap don't work. When the camera is set at AF-S, the camera does not take photo because it thinks focus has not been achieved. When the camera is set at AF-C or MF, the camera takes photo regardless whether focus has been achieved.
- With screw-AF lenses (DA 40, DA 70, and Sigma 50 macro), the camera thinks the lens + tube combo is screw-AF and tries to focus (of course to no avail). The grinding noise of the camera's AF motor is loud and annoying.
When I use a piece of Al foil between the tube and the lens to ground pin 7 (at 12 o'clock position of the tube on the left in photo above), those two problems go away.
Last edited by SOldBear; 06-29-2012 at 11:22 PM.