I recently shone a torch through one of my lenses (which looks clear and takes fine pictures) to see that the top element is extremely fogged up inside. Question is, does this affect the ultimate lens image. Should I get it cleaned?

-- Karl Yik (karl.yik@dk.com), March 25, 2002

Answers

This is a very common topic here. My experience with the fogging is that is does affect contrast especially at wide apertures, and does increase veiling flare in backlight situations. I had a 135mm Tele- Elmar cleaned, as well as a 35mm Summaron, and the results were noticeably improved especially at the wide F stops. Better contrast, color saturation, less flare. Stopped down and in many shooting situations, a light haze will not deter from the image quality.

Warning: Sometimes the fog is not something that can be cleaned off-- it can be a failure of the coating itself. I had this happen on a DR 50 Summicron and an old Zeis Sonnar, and the correct repair (recoating two elements) would have cost as much as the lenses were worth.

-- Andrew Schank (aschank@flash.net), March 25, 2002.

Older Leitz lenses used organic lubricants made from animal oils, believe it or not, and after time these oils can deposit on the inner surfaces of the lens. Not only does the lens get fogged, but the lubricants for the aperture and focusing mechanisms dry up. Get the lens cleaned and relubricated properly.

-- George Huczek (ghuczek@sk.sympatico.ca), March 25, 2002.

Check out
http://www.camer aquest.com/mlenses.htm#Fogging

Mike

-- Michael Kastner (kastner@zedat.fu-berlin.de), March 26, 2002.

Check out http://www.camer aquest.com/mlenses.htm#Fogging

So much for the whale oil blubber explanation! Thanks for the link.

-- George Huczek (ghuczek@sk.sympatico.ca), March 26, 2002.