Bobfrance and fidget.
Thanks for the link to the manual. It is for the GA645i which I guess is a very slight evolution from the GA645. Checking the manual confirms that, if I understand correctly, the only way to not having the flash firing any time is to stay in the programmed AE mode with good light (it will fire automatically in low light). In manual exposure and aperture priority, the flash will "always fire" to quote the manual regardless of the flash being (manually) popped-up or not. A hint is that in those latter exposure modes, the calculated exposure does not change whether the flash is popped-up or not: in any case, the light emitted by the flash is taken into account into the exposure. Another point is that if the picture is taken, the flash not being popped-up, it seems that it fires anyway and there is a strong smell of heated plastic... I guess I shouldn't do that anymore. I have to check the actual underexposure (film returning soon from the lab) when used that way. So probably there is no official means to override this automatic flash, but I will try to investigate further: maybe cutting a cable somewhere could do the trick?
Compared to the GS645, which I have never held, the overall impression seems very comparable; the main difference being the wider lens (and maybe better coated) on the GA645 and the much finer (at least to my eyes) "mechanical look" of the GS645. And of course autofocus! My eyesight recently declining, autofocus seemed the way to go, over other MF rangefinders I had once considered such as Mamiya 7 (II), Bronica RF6454 and Mamiya 6.
