I just have my flash meter back from a friend, so I can check and reply to
someone who said the 90/2 is 2/3 stop slower than the 85/2 at maximum
aperture. Following is the test setup and result:
1. Flash test 1.
-OM4 with test "film" came with my OM4Ti covered the shutter, ISO 50.
-T32 on camera hot shoe + ND8 filter
-focus to just cover two 8x10" Kodak grey card (magnification fixed).
-Sekonic flash meter to record the reading.
-All lenses set at F2.
Result:
85/2 ---- EV2 +0.3
90/2 ---- EV2 +0.1
100/2 --- EV2
2. Flash test 2.
Same setting as above except focus on a cloth of 2m away (distance fixed).
Camera ISO 50
Result:
85/2 ---- EV1.4 +0.4
90/2 ---- EV1.4 +0.4
100/2 --- EV1.4 +0.5
3. Ambient light test.
-OM4 with test "film" came with my OM4Ti covered the shutter, ISO 100.
-Focus on plain wall 3 meters away (indoor window light).
-Reset and set memory lock for each test (use camera's OTF, OTC average
metering)
-All lenses set at F2.
Result:
All lenses have the same reading of 1/30s. Please note that camera can only
resolve to 1/3EV.
>From the above results, it is clear that all three lenses are very close in
max aperture.
C.H.Ling
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