On 2013-01-02, Doug White wrote:

[ ... ]

In more sophisticated 35mm SLR film camera systems, you could set the
aperture, and the exposure could be controlled by quenching the flash
when enough light had hit the film. By not completely discharging the
flash cap, they could recharge the flash faster as well. My Olympus OM-2
did that if you used the Olympus flash designed for it.

Same with the Nikon N90s.

They actually
had a sensor in the camera that looked at the amount of light hitting the
film.

Nikon did the same. The film made a nice diffuse reflector, so
the sensors in the bottom of the box between the film and the lens could
get a good reading.

I haven't paid much attention to the inner working of the newer digital
cameras, so I don't know at what price/quality level they might start
playing those sorts of games.

When Nikon went to the DSLRs, they could not use the same trick,
because the sensors did not generate the diffuse reflection needed, so
they started using a low powered pre-flash (fast quench) to meter with,
and then a full-powered flash (or at least as full-powered as needed)
for the actual exposure.

They first discovered this with the Kodak conversion of the N90s
film camera to a digital with a special back, so they had to use other
exposure methods built into the flash. IIRC, the best flash for that as
the SB-28.

Enjoy,
DoN.

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