clivengu: No, an A100 with F42 mounted cannot trigger an off-camera F42 in TTL (unless there is an optical slave trigger attached to the bottom of the off-camera F42) but then it would not be working in TTL anymore.
To prove your point, I would suggest having a picture where the A100 + F42 is looking at a mirror. The off-camera F42 then exposes its flash foot to the camera to show no optical slave triggers. The picture would show the A100 + F42 and the off-camera F42, with their wide-angle panels pulled out, to show that it does light up.
Understandably there are times you think it triggered but it actually did not as the flashes can be confusing.
Let me go through this again:
Minolta 7 (
film) - can use the F56 to trigger off-camera flashes (this is why there is that option but the protocol was not supported with digital bodies)
KM5D/KM7D/A100-A550 - can only use the pop-up flash to trigger the F36, F56, F42 and F58 off camera
A700 - can use the pop-up flash or F58 on camera, to trigger the F42 and F58 off camera
A850/A900 - can use the F20 or F58 on camera, to trigger the F36, F56, F42 and F58 off camera
nope, only using the built in flash on your A200 can trigger off camera flashes (F36/F56/F42/F58)
but hey, do get the F58, then you can do wireless with multiple flashes!!
i know~ but i tot getting the f58 for bounce flash on camera with f42 off camera mar~