That is the different between good quality lens and poor one, some years ago
I bought a used Sigma 600 that has peel off of reflective coating on the
mirror near the edge. At first I don't know it is a coating peel off, I try
to clean it by disassembly the lens. Do you know how the front focusing
group is fixed with the focusing ring?.... they use tape... yes tape, there
is also a light guide (or shield, I don't know how to call it) at the center
of the mirror. How it was fixed? I think they have used silicone sealant, I
slightly pushed it and it came off! Finally I put everything back, pay with
it for a few weeks and then sold the lens to another shop.
Few years later I saw from the net that people complaining the big Sigma
lenses, I remember one of it was 500/4.5 the AF version, they said the front
group was fixed with tape and the tape loosed, when the lens focus the front
group dropped to the ground!
C.H.Ling
----- Original Message -----
From: "Clemente Colayco" <litefoot@xxxxxxxxxxxxxxx>
> I own and have used hand held a Sigma 600 mm F 8 mirror lens. It gives
> decent results hand held at higher shutter speeds. The only problem is
that
> after years in storage one of the internal lens elements developed a
hazing
> discoloration which seems unremovable. So its now waiting for some
magician
> that can erase it.
>
> Regards
>
> Titoy
>
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