I had bought a 300mm f4 L used lens several weeks ago. When I had examined
it in the sunlight etc it looked well, no marks on the front glass, perfect
finish etc. Last night I happen to have it out and looked at it with front
and rear caps off over a bedside lamp that happened to have been on. Anyway,
with the light bulb at the rear of the lens and looking through the front I
was somewhat surprised to see a good deal of dust and junk that I had not
noticed when examining it before. I used the lens once and it worked fine
and gave good slides.
It is hard to tell where the dust lies. It is not on the front element since
I used a blower brush to clean it. I am not sure how much of the dust/debris
or whatever is on the rear element vs on the inner elements. I was a little
nervous about sticking a blower brush into the rear opening of the lens to
clean it since I didn't know if this element was recessed because it was more
fragile, sensitive, less coated etc. Is it safe to insert a blower brush etc
into the rear of this lens for cleaning? How can the back element be fully
cleaned? If there is still dust and debris visible on transillumination with
a lamp, will it affect picture quality and is it normal to see this type of
dust when illuminating it this way ? Is it common to see it this way and not
by examining it in the sun? How should a used lens best be examined? Lots
of questions.
Thanks.
Howard
[EMAIL PROTECTED]
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