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[OM] Filters, revisited

Subject: [OM] Filters, revisited
From: Gary Reese <pcacala@xxxxxxxxxxxxx>
Date: Tue, 29 Aug 2000 15:42:06 -0700
I promised some more SQF tests with and without filters.  Here are two,
albeit at maximum aperture only - which is the aperture that the defects
are most pronounced at.

85-250mm f/5 Zuiko
OM-4T with mirror and diaphragm prefire, sample 2
@ 250mm setting
Vignetting = B- @ f/5 with filter, A- @ f/5 without, A- @ f/8, A
thereafter
Distortion = moderate pincushion
Aperture  Center    Corner
f/5*      C+        C+
f/5       B         B-
f/8       B-        B-
f/11      B         B
f/16      B         B-
f/22      **        **
f/32      **        **
Notes: * = with Hoya Skylight filter, which exhibits moderate contrast
images. Moderate contrast at f/16, moderately high at f/5-11. ** = no
SQF or contrast data available at f/22-32.

In short, the Hoya filter caused light fall-off and a reduction in SQF
grade, primarly due to a contrast loss.

100mm f/2.8 Zuiko (multi-coated)
OM-4T with mirror and diaphragm prefire
Vignetting = A- at f/2.8, A thereafter
Distortion = slight pincushion (none?)
Aperture  Center    Corner
f/2.8*    D         C
f/2.8     C-        B-
f/4       B         B
f/5.6     B+        B+
f/8       A-        B+
f/11      A-        A-
f/16      B+        B
f/22      B+        B
Notes: * = with a Canon 1A filter, which exhibits low contrast images.
Moderately low contrast at f/2.8 without filter, as well as f/4 and
f/16-22, moderate contrast at f/8-11, moderately high contrast at f/5.6.

Again, lower contrast and SQF grades . . .

As the Monkees sang: "I'm a believer, I couldn't [use] her, if I tried." 

Gary Reese
Las Vegas, NV

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