I just wrote a quick reply but it is not showing up, so I will write it again. Oh boy, I should have copied it. I will write it all over again, arghh.

First, thanks Chris Crawford for the interaction and answering the questions.

So I believe you are saying that one need not care about the focusing because when using the flash unit it is about the distance the flash is from the subject. So in other words, here when using the flash focusing is irrelevant but distance and position with the flash is how it works. Am I right so far?

Now I would think that the higher number the aperture (i.e., f16, 22) would give the photograph a depth of field.

I still cannot grabble around the idea that flash users are shooting at 1/50s of a second hand held, would that not cause blur in the photograph or does the flash compensate for that?

Also, here's a hypothetical situation: I have the Leica M6TTL with the flash mounted in TTL mode, and I am in a low light situation. The ISO is set at 1600, my subject is 3.4 feet (1 meter) away from me. I have the aperture set at 16 which the flash on the back gives me the distance of 23 feet. Now that is a lot of feet that it covers, but my subject is only 3.4 feet. Would the TTL know that my subject is 3.4 feet away and give me the correct exposure or does my subject have to be 23 feet away when I shoot the camera?

Does the SF20 Flash unit in TTL mode dictate my aperture, or do I choose the aperature and the SF20 adapts to that giving me the correct exposure.

I hope that I am asking the right questions, and I am not in some other world.

Also, what is the order. You see the subject, the subject is 4 feet away, in the TTL mode what would one do next. I am a bit confused.

I'm thinking that since the TTL acts as a automatic flash, I would just shoot the camera 4 feet away from the subject without focusing (because that is superfluous) at f16 with the ISO at 1600 (can't change that) because I am in a low light situation.

I hope this is right if not, I need correction.