Hello and happy new year. I have a lens here that shows a very colorful ring (gold,purple,blue) around the front element at the rim of the glass when I hold it under a light and rotate it. There is also some similar thing happening at the rear element as well but not all the way around, again at the rim but not continuous,four areas about 1/2-3/4 inches long. Also as I was inspecting the pretty colors I noticed something loose in the front element. If I hold the lens (front element only) in my hand and rotate it briskly I can actually feel and hear something spinning. Can anyone tell me what these problems are, if they are a problem and if they can be rectified without taking out a loan. Thanks in advance and again, Happy New Year!
The "colorful ring" is indicative of lens separation. Cemented elements have become "uncemented" or separated at the edge of the glass. Because the separation is a very tiny distance, the colors are the result of light wave interference and occur much in the way rainbow patterns do when a thin film of oil is on the surface of water . The separation may possibly have little effect on the image, especially if the lens is stopped down to a working aperture. Its effect may be principally on the resale value. Or it could possibly affect the image. Without seeing the lens itself, it's difficult to tell. Lenses can be recemented, but the cost may be more than the lens is worth. It depends on the lens. Again, not knowing what the lens is makes it impossible to tell.
The lens is a Rodenstock Sironar 360mm f6.8 in a Compur 3 shutter that I just got off Ebay. It was listed as "Mint Condition"," " Pristine" and of "Professional Quality". Sorry for not putting that info in the original post,Cheers.
This is not at all uncommon with older Sironars. I had a 150mm f5.6 that I got in a trade for some old odds and ends I no longer needed. The lens turned out to be one of the sharpest I owned and I made many wonderful pictures with it until I decided to get rid of it in favor of something a bit smaller and lighter. The separation never seemed to advance further toward the center of the lens and as far as I could determine, was never a factor in my results.
http://www.focalpointlens.com/ can recement and even recoat your lens - other camera repair shops send their lenses to him as he has very specialized equipment and training. He did Leica and Rollei-Zeiss repairs for me, and he knows what he is doing.
But he isn't cheap and I would raise heck with the seller about this.
The lens in its current condition is only worth $200 or so - repaired it is easily a $500 lens, so you might justify repairing it - but the seller should pay at least half!
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