I have done another series of tests of viewfinder brightness and these results
look much better; I think the flash in the previous test was introducing too
much variation.
Test goal: To measure the difference in viewfinder brightness between the
earlier OM cameras and screens (OM1 and OM2) and the later cameras and screens
(OM2s, OM3 and OM4) by metering the light transmitted through the viewfinder.
Test setup: Camera on a tripod with a 50mm1.8 lens aimed at the ceiling. The
ceiling was illuminated the halogen flood lamps.
A varimagnifinder was mounted on the camera. Metering was done with a Minolta
IV-F meter, NOT with the camera meters. The meter has a reflective light
adapter which meters the same angle of view as a 50mm lens. The meter was used
to measure the light transmitted through the viewfinder of the cameras by
placing the sensor head in the cup of the varimagnifinder. Four measurements
were taken with each combination of camera/screen and illumination on the
ceiling was measured before and after each series to ensure the subject
lighting did not change.
So this test measured the light transmitted through the viewfinder; the camera
meters were not used at all.
Metering the ceiling directly (not through the viewfinder) gave a reading of
F16.6 @1/2 second (ISO800) for all runs. The Minolta meter uses a scale where
fractional F stops are reported as decimals, easy to understand if the F stop
is a whole number (i.e. F16) but a little weird on fractional stops (i.e. F5.6).
A reading of F16.5 is half way between F16 and F22, A reading of F5.6.5 is half
way between F5.6 and F8; if the stop is less the F11 the stop is reported as a
decimal (i.e. F8.0) so some readings have two decimal points. The meter
settings were not changed for the viewfinder measurements (1/2 second ISO800).
OM2s with Beattie Intenscreen gave a reading of F5.6.2 through the viewfinder;
with a 2-13 a reading of F5.6.2; with a 1-13 F4.0.7.
OM1n with Beattie screen gave a reading of F5.6.8, with a 1-13 F5.6.2.
For you statistics fans the only series which had any variation was the OM2
with Beattie which gave two readings at F5.6.2 and two at F5.6.3.
Conclusion: The 2-x and Beattie screens brighten the viewfinders by 1/2 stop.
The OM2s, and by implication OM3(T(i)) and OM4(T(i)) viewfinders are 1/2 stop
darker than the OM1n and by implication OM1 and OM2(n). The brightest
viewfinder was the OM1n with the Beattie screen but this requires handheld
metering or meter adjustments. And the later cameras with later screens are as
bright as the earlier cameras with earlier screens.
I may put a Beattie screen in a OM1n for situations where I am not relying on
the camera meter; i.e. macro where I use the meter as a flash meter and
compensate for magnification. Also if you do night shots by guess and
experience (as good as metering usually) a similar setup might be useful.
I apologize for the earlier post which did not completely explain the procedure
or what was being measured.
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|