Matt King thanks again, you're very kind. I read the same manual, yet either I am very slow at learning or the manual writes as bad as I do. Probably both and hence my confusion.

Now, when the manual says "expected" maximum it means that I can shoot the subject from anything under 23 feet. Now, you're saying that the TTL circuitry automatically adjusts the light output for distances. Wow, then the manual mode may be superfluous, except in scenes where the TTL may have a hard time reading.

So, I can conclude since the photographer chooses the aperture in the TTL mode, the flash increases in output or descreases the flash depending on the aperture the photographer chooses. So the SF20 flash in the TTL mode adapts to the photographers desired f-stop setting.

I think it is clicking.

Matt is this correct?