>
> In article , C.H.Ling <chling@xxxxxxxxxxxxxx> wrote
> >
> >Below 1/60s reflect from film, above 1/60s reflect from shutter curtain.
> >
> Its not quite as binary as that CH. At 1/60s around half the exposure
> is metered from the shutter curtain and half from the film.
>
> Consider what happens as the shutter opens - the meter starts
> integrating reflected light as the first blind traverses across the
> film. At first all of the light is reflected from the blind, half way
> open it is reflected from the blind and the film, and finally when fully
> open all the metered light is reflected off the film. A short time
> after the blind is fully open, enough light will have been metered to
> trigger the trailing blind release - ending the exposure to each part of
> the film as it traverses the focal plane.
>
> At 1/125s around 75 0s metered from the blind and 25 0.000000rom the film.
>
> At 1/30s around 250s metered from the blind and 75 0.000000rom the film.
>
This is only the thing that you see, not necessary what the computer inside
OM4Ti is doing.
I have just performed an experiment, with a Zuiko 100/2 and OM4Ti mount on
tripod, focus to plain wall. Without inserting film, in auto mode, adjust
the aperture to let the reading goes to 60s+1/3 stop, turn memory on,
trigger the shutter, the memory read 60s+1/3.
Clear the memory, adjust the aperture again to let the reading goes to
60s-1/3 stop, turn memory on, trigger the shutter and read 8s+1/3.
If the curtain is take part in the light measurement at below 1/60s. I
don't think the reading will drop that much, according to your theory more
than 75% (or over 90%) of light should come from curtain reflection.
May be this happen only to my 4Ti, much appreciate if you can try your own.
C.H.Ling
> The actual ratios are a bit different, because the blind travels across
> the focal plane in less than 1/60s, but you should be able to see the
> principle - the transition from metering on the film to metering on the
> blind is gradual, not as sudden as you seem to indicate.
> --
> Kennedy
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