What is this???

[stantheman13]

This seems to be on the rear element of a Graflex Optar....135mm f:4.7. It is a ring of haze/mist/abrasion....center is clear. The rest of the lens is good. Was this caused by bad cleaning over the years? Delamination ( seems odd to be a perfect ring..bad cleaning would not cause this...and it seems to not be on the surface )?

Thanks all! I'm new here, but I've been a pro photographer for 35 years....my site: stanwanphoto.com

[IanG]

Have you got condensation inside the lens, I've seen this with enlarger lenses.

Ian

[N Dhananjay]

Probably from the cement crystallizing. Elements in a group were usually cemented in place. Sometimes the cement starts going bad, either because it is old and/or was subjected to some kind of stress (e.g., extremely cold weather etc.)
Cheers, DJ

[E. von Hoegh]

This seems to be on the rear element of a Graflex Optar....135mm f:4.7. It is a ring of haze/mist/abrasion....center is clear. The rest of the lens is good. Was this caused by bad cleaning over the years? Delamination ( seems odd to be a perfect ring..bad cleaning would not cause this...and it seems to not be on the surface )?

Thanks all! I'm new here, but I've been a pro photographer for 35 years....my site: stanwanphoto.com

Hard to say, without actually having the lens in hand.
That's a Tessar type lens, the rear is comprised of two elements cemented together. Is it on the inner surface of the inner element? Or in the cement between the elements? If it's not on the surface of the glass, it wasn't caused by careless cleaning.

[BrianShaw]

Ay carumba... that's scary looking!

[Nathan Potter]

Santa Maria! Looks like a classic example of a structural change in the bonding material between two elements - if it is actually between two glass elements.
Technically I would guess that it is a stress induced ring as Dhanjay has suggested, possibly (even likely) due to cycling through the glass transition temperature. Not necessarily a crystalization or phase change phenomena but maybe just a stress cracking due to the dramatic change in physical properties that can occur when a polymer or Canadian Balsam moves thru the glass transition temperature. That temperature is low for some polymers and in the case of Canadian Balsam is around 40 degree C. Sometimes it takes repeated cycling to gradually haze the lens. The circular ring pattern certainly suggests a stress induced phenomena related to the shape of the lens and a pattern that is unlikely to be from some external contamination.

Nate Potter, Austin TX.

[stantheman13]

Thanks everyone for the replies.....yea it's between the two rear elements, because I don't see it on the outer surface....seems to be internal.....and probably because it was in a cold environment for a long period of time. I'm guessing there's nothing I can do about this....the lens is now junk? Or can be used as a soft focus lens? lol.

[Nathan Potter]

The lens pair can be re cemented; not a trivial task but there has been a recent thread here somewhere that describes a home made process for separating two lens elements, cleaning them then re cementing. Can use either canada balsam or a UV curable polymer as the cement.

Nate Potter, Austin TX.

[stantheman13]

If someone has the link to the post please put it up.....I've looked and don't see one one taking the lens elements apart.

[Nathan Potter]

Steven Tribe has reported on doing this. See his thread of 5 Feb 2010 on LF DIY section, "How I did it:new balsam for RR". (Rapid Rectilinear). You may find related other posts or threads by him on the subject which can lead to other references.

My opinion is that the process is not difficult if you are an experienced technical person used to building precision hardware.

Nate Potter, Austin TX.

[stantheman13]

My problem is the rear lens elements are held together with the knurled black outer ring as seen on the photo at the thread beginning. Is this threaded on the brass body? I've never taken apart a large format lens before and I don't want to do any permanent damage.

[Nathan Potter]

I have not disassembled an Optar like this but I would guess that the knurled ring needs to be unscrewed to access the rear element. You may want to remove the lens from the lens board before starting the disassembly. Expect that knurled ring to be difficult to remove. Others here may have a more definitive answer about your Optar.

NatePotter, Austin TX.

[E. von Hoegh]

My problem is the rear lens elements are held together with the knurled black outer ring as seen on the photo at the thread beginning. Is this threaded on the brass body? I've never taken apart a large format lens before and I don't want to do any permanent damage.

The "knurled black outer ring" is the visible part of the mounting for the rear cell of the lens, it will unscrew from the shutter. On the inside, there will be either a retaining ring, holding the glass into the mounting, or the edge of the mounting will be turned over to retain the glass.
If you can get the glass out of the metal mounting, it will be possible to recement the glass. This lens may use balsm, or it may use another type of adhesive.

[Steven Tribe]

I have looked at the cell mount for some Wollensak raptars (version of the optar, I think). These have been very professionally sealed with a compressed alloy edge.
There is no obvious way on these to get at the glass lens. In fact, it looks impossible as there is a protruding part of the lens (1mm) which makes mechanical (file/saw) very difficult. This is often the "no-go" problem for cement replacement.