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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