Conventional wisdom would say that a lens with fine cleaning marks and some
coating loss from ALL its elements surfaces (apparently due to an aggressive
fungus removal) would perform poorer than one in excellent condition. I had a
chance to make a side by side comparison and the results were surprising: no
significant difference between the two. Here is the results of that
comparison, which I'll be putting up on my WWW site. The first in each pair
of SQF values is the user grade lens and the second the excellent condition
lens.
85mm f/2.0 Zuiko (single-coated)
data for two examples (7 condition,9 condition)
Vignetting = A
Distortion = none
Aperture Center Corner
f/2 D,D C,C-
f/2.8 B,C+ B,C+
f/4 B,B- B-,B-
f/5.6 B,B B-,B+
f/8 B+,A- A-,A
f/11 A-,A- B+,B+
f/16 A-,B+ A-,B+
Note: 7 condition lens with coating loss due to fungus removal treatment,
shows moderate contrast images; 9 condition lens shows contrasty image. Fine
detail evident in bothe lenses stopped down. SQF grade differences are
insignificant between lenses at all apertures.
Gary Reese
Las Vegas, NV
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