Hacker
黑客
What is this outer ring at the rear of the lens?
Meleica
Well-known
looks like lens separation - failure of cement....
Dan
Dan
ferider
Veteran
I think it's bubbles between glass and metal, where the rear element is cemented into a metal ring. So yes, separation, but not between glass elements, so results should not be affected. Quite frequent in vintage lenses.
Roland.
Roland.
Hacker
黑客
Would a CLA be able to solve the separation? It looks quite bad from the pictures.
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ferider
Veteran
Not as part of a normal CLA, but John (at Focalpoint) can probably fix it. Best is to email/call him.
But again, this is rather frequent, not normally considered a defect, etc. John might wonder why it bothers you.
Roland.
But again, this is rather frequent, not normally considered a defect, etc. John might wonder why it bothers you.
Roland.
raid
Dad Photographer
Which lens is it?
I would just use the lens first to see how the decementing affects the images [or not].
I would just use the lens first to see how the decementing affects the images [or not].
dberger
Established
Ahh, Mr. Quinon I presume.
As this is a Sonnar, the rear group is a cemented pair. So, glass separation is possible, although I do not think that is what you have; what you see is too uniform and only at the edges.
My copy of this lens does not show these marks, but does show an angled seating ring upon which the rear cemented group rests (see diagram from Rob here http://www.rangefinderforum.com/forums/showthread.php?p=980504#post980504). So, I think Roland is correct -- the contact between the ring and glass is probably separating. Or something has migrated between the ring and glass. Either way, this happens frequently enough on old lenses, and I would not worry about it unless something sounds loose, the "problem" gets worse, or images do not look right.
Cheers,
David
As this is a Sonnar, the rear group is a cemented pair. So, glass separation is possible, although I do not think that is what you have; what you see is too uniform and only at the edges.
My copy of this lens does not show these marks, but does show an angled seating ring upon which the rear cemented group rests (see diagram from Rob here http://www.rangefinderforum.com/forums/showthread.php?p=980504#post980504). So, I think Roland is correct -- the contact between the ring and glass is probably separating. Or something has migrated between the ring and glass. Either way, this happens frequently enough on old lenses, and I would not worry about it unless something sounds loose, the "problem" gets worse, or images do not look right.
Cheers,
David
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laptoprob
back to basics
Hey, another Quinon!
I had separation in mine some time ago. Mine looked different though.
Started a thread on it. The lens is a puzzle to take apart but you will learn. The rear block is cemented. Will come loose easily in warm water. Then recementing. That is the only part I had done.
Reassembly is in reverse order...
I had separation in mine some time ago. Mine looked different though.
Started a thread on it. The lens is a puzzle to take apart but you will learn. The rear block is cemented. Will come loose easily in warm water. Then recementing. That is the only part I had done.
Reassembly is in reverse order...
From the way the spanner wrench slots are mutilated, it looks like someone was already inside that lens, and either had the wrong tool or used considerable force to open it.
laptoprob
back to basics
Checked mine. Also has a ring inside the glass, but all neat black. This is a coating applied after re-gluing the rear block. You still have the old coating on it. May be hardened, flaky or coming off. No worries as long as the lens is clear.
How many Quinons do we have here at RFF?
How many Quinons do we have here at RFF?
Seele
Anachronistic modernist
It does not look like a physical "ring" but more like a constriction in the cemented group, and the bubbling is due to the degradation of the edging paint.