Tom, others...
This Olympus would have to answer exactly....at any rate for the scheme to
work
properly the nominal reflectance of the film should closely match the curtain
pattern. Provided the gain in the current amplification scheme picking up the
silicon photo diode current is properly calibrated to the actual
reflectance of
the target, it doesn't really matter what the actual value is. You'll get the
proper exposure. I would be surprised though, if the curtain pattern is too
far
from 18%, but perhaps on the high side due to how densely its populated with
pixels. You could compare a spot meter reading off a piece of film to a grey
card to satisfy your curiosity.
By the way, another scheme, but one which uses only the curtain reflection, is
white spot used on the first shutter curtain of the Leica M6. Check it out
some
time. You have to cock the shutter to see it.
K
In 01:44 PM 12/10/99 -0500, you wrote:
>Hi Kurt, others
>
>Is the average the 18%, or is it some other number? Gary?
>
>Tom
>On 9 Dec 99, at 10:50, Kurt Hurley <olympus@xxxxxxxxxxxxxxx> spoke
>about "Correction: film reflectance was Re," saying
>
>Tom etc.,
>
>...
>is then used for determination of longer exposure times. Contrast
>this with the reflection off the pixilated white paint pattern of the
>shutter curtain (approximating an 18% reflectance) at speeds 1/60 and
>higher . As the shutter speed gets higher and higher and the gap
>...
>
Kurt Hurley IDS 2000 Product Marketing Manager
Schlumberger T&T - Diagnostic Systems
1601 Technology Drive San Jose CA 95110
email khurley@xxxxxxxxxxxxxxxxxxx
PH 408-437-5156 FAX 408-437-9031 PG 408-699-4587
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