Don,
> I have an original RTS, short for "Real Time System". I never saw any > reference to the speed of the shutter response, in any literature. > What I did see was the claim, which is true, that the shutter speed is > set just at the instant of exposure.
I'm not quite sure what you man by "the shutter speed is set just at the instant of exposure", or what you think that means. That is the way any automatic camera operates, as far as I know.
To quote directly from the RTS I brochure:
"Real Time is taken from computer terminology. It means the total absence of physical time-lag in the distribution of information." And from reading the brochure, they simply mean that all the information is instantaneous (as opposed to a system like the Canon F-1) for both the display and for the computations it does to choose the shutter speed, and that it was specifically designed to reduce the time from pressing the shutter to exposure.
The metering SPD is located directly above the viewfinder eyepiece, so it can only operate with the mirror down...so the RTS does not operate as was mentioned by someone else (adjusting the shutter speed after the aperture is stopped down). In fact, the brochure gives the sequence of events when the shutter is pressed:
"Depression of the shutter release button activates a micro-switch which instantly energizes an electromagnet and starts a chain-reaction... It activates the TTL full aperture light reading system; triggers the movement of the reflex mirror; stores the light reading information in the memory register; stops down the lens diaphragm to the preselected setting and releases the focal plane shutter."
Note, the meter is read BEFORE the aperture is stopped down, and quite a few things happen between the selection of the shutter speed and the opening of the shutter...so it's not really, in camera time, "just at the instant of exposure"...not that it isn't close, or that it really matters, but I think that terminology doesn't outline what really happens, as some cameras may in fact (someone mentioned the OM-4 and a few others) may compute the shutter speed as the last thing before opening the shutter.
I guess it depends on what one thins of as an "instant". For some, it's an eternity (I deal in pico second designs), and for some, it's a lifetime...
Regards,
Austin