I received an off-list e-mail inquiring about the possibility of using the
little Hakuba slide viewer that I posted about last week as a light source for
the inspection of lenses for fungus, dust, and so forth. With only moderate
verbosity, I expressed my opinion, then proceeded to opine further about what I
considered to be the proper way to check the innards of a lens.
Then I got to wondering if my advice was as good as I thought it was when I
wrote it. Since we're all, at least those who remain true-blue OM users, now
in a position of dealing almost exclusively with used gear, often bought
sight-unseen based on a description by a total stranger in a faraway place who
may be either ignorant or dishonest, or both, we need to know how to inspect
the gear properly. It seems we're hearing more and more about problems with
lenses bought over the internet from some in our group.
Anyway, this is what I wrote, and if anyone has any disagreement, any
correction, or a better modus operandi, I think it would benefit us all to hear
about it. I can't always be perfect, you know, and do occasionally learn a
thing or two here.
"The little Hakuba slide viewer is definitely NOT the tool you're looking for
to inspect lenses. The best way to spot nasties inside a lens is by shining a
plain old flashlight through it, from each end, while moving the light and the
lens around. Like the focused beam of light from a slide projector shows the
dust floating in the air, all of which was invisible in the diffused room
light, the focused beam of the flashlight sharply reveals the crap inside a
lens.
"As an experiment this morning, I used both the slide viewer and a two-cell
Mag-Lite to look at the only lens I have that I know has an internal problem, a
65-200/4 Zuiko with the all-too-common bad element toward the back. With the
diffuse light from the slide viewer, had I not known about the bad element,
chances are better than good that I would have overlooked it. With the hard
light from the Mag-Lite, the frosting of the element was immediately obvious,
as
was every speck of dust inside the lens.
"In fact, using a flashlight to look inside a lens, particularly a zoom lens,
can be a scary experience. It puts me in mind of a line from an old Rod
Stewart song: "The morning sun, when it's in your face, really shows your age."
Almost every lens has at least one or two specks of dust inside, and a hard
light source, just like a projector in a dark room or the sun on Maggie May's
face, shows things that soft, diffuse light won't."
Walt, standing by for correction
--
Everybody thinks they have a sense
of humor -- even people who don't.
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