Is this fungus?
If it is a mirror lens, it might be decay of the mirror coating that you can see.
Whatever it is, it does not look good.
If I look through the front I can justmake ouot the "stain" at the far end of a tunnel.
If I rotate the focus whilst looking through the front the "stain" doesn't rotate but a dust spec on the mirror does.
If I look through the back the "stain" appears just below the glass surface and doesn't rotate when the focus is moved.
From the above I've deduced that the "stain" is not on/in the main parabolic mirror or the small secondary hyperbolic mirror, both of which rotate with the focus.
It therefore is on the inside surface of the back lens or the interface of two glasses, assuming the back lens is multi-layered.
I haven't figured out how to get at it yet, but having heard so much about fungii on this forum, and as far as I know never experienced it, I thought I'd ask the question.
As I said it didn't cost a great deal so ......
regards
Bernard
In that case, it could be fungus, or the "glue" in the optic sandwich failing.
Normally Fungus on lenses are round growths in areas of the glass, this could be one large growth.
However, it is unusual and possibly someone might have the correct answer.
With the camera on a tripod I get the same exposure setting with my Tamron and this lens, so it isn't as dark as it might appear.
It does have a slight milky tone which doesn't come out in the 'macro' shot of the monitor and some of the fuzziness could be down to a tripod sat on carpet at the other end of the room.
regards
Bernard
cheers
bb2
K5, K20D, Bigma, Sigma EX 105, Sigma EX 10-20, Sigma EX 28-70 F2.8, Sigma Ex 1.4TC,
Pentax 135 F3.5, Pentax 30mm F2.8 , Pentax 50mm F1.7, Pentax 55mm F1.8,
Super Taks: 35mm F3.5, 50mm F1.4, 135mm F3.5, 200mm F4
Vivitar TX 200mm F3.5,Vivitar (Komine)135mm f2.8, Vivitar 2X TC, Vivitar T4 400mm F6.3
Tamron SP 35-80,80-210 F3.8, Helios 44M, Mir 1B 37mm F2.8, Jupiter 9 85mm F2, Chinon 28mm F2.8, 3M-5A 500mm F8 etc etc
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -
I think this is separation between a couple of the correcting lenses. Have it on my 350mm F5.6 mirror.
+1 (and I've also got it on my 350mm/5.6 mirror if that's any consolation!). I'm pretty sure it's not fungus, as others have said. Even in a really heavily fungus-infested Sigma zoom I saw, there were thread-like filaments at the edges.
I'm sold on the idea of it being between two lenses and as I've discovered there is no appreciable light loss.
Coupled with the fact that despite spending time making a 55mm pin spanner to remove what I think is a locking ring holding that section together to find that I cannot budge the ring. It's either glued in, or Al-Al bonded itself into place.
So I'll just put up with it.
Next job is to test it for resolution/clarity, but as it doesn't focus on infinity I'm waiting for the postman to deliver a flush fit M42-PK adapter, then I'll be able to play outdoors rather than with a 13mm extention (hence the monitor shot).
regards
Bernard
Naturally, not all defects are equal, and some will add distortions to the image that are out of proportion to their apparent size, conversely, sometimes "terrible" damage won't appear in the end image. It's why a damaged lens at a good price is often worth putting on the camera to see what actually has happened to it!
I agree, many years ago I bought an enlarger to do B&W printing. The condensor lens had quite a large chip out of one side (probably been dropped) but this made absolutely no difference to the prints. I accept that a condensor is not on the image side of the negative.
Bernard
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1776 posts
15 years
Burton upon Trent
It's not a patch on my Tamron 500mm mirror but at the cost it looked worth playing with. It's slightly blurred as the following macro (ish) shows
regards
Bernard