Weird haze from lens.

IcedTea · Dec 24, 2011

My dad had some leica lenses from the 1970's that haven't been used for more than a decade. I was able to clean the dust off them with an anti static brush and an air blower. All of them shoot very well except one of them, the Summicron 50mm. It seems to have a yellow haze from just looking in the rangefinder, something that the rest of them don't have. What could cause this?

MLeeK · Dec 24, 2011

I have heard this before on old lenses. The trick to "fixing" seems to be to put it in the sun-on a windowsill. I have also heard of putting tin foil inside the back cap as this will speed the process/amplify the sun's effect.

unpopular · Dec 24, 2011

What Leek is talking about here is thoriated lenses. I just read that early summicrons use thoriated glass (http://www.rangefinderforum.com/forums/archive/index.php/t-89263.html) It really isn't that big of a deal, and placing it in the sun for a couple months will help the problem. If shooting black and white, thoriated lenses allow for an extremely good yellow filter. If shooting digital, you can just correct it with auto white balance, which is what I do with my Canon FD 35/2. I also suspect that it might help with cloud definition in wide shots, and probably will serve as an excellent UV filter since any UV energy entering will be absorbed and used in whatever atomic process that is also turning thoriated glass clear again in the sun.

One intersting factoid is that thoriated lenses are radioactive. It emits a small quantity of harmless radiation, but COOL nonetheless.

If it is throaited glass, this yellowing should be completely translucent and not foggy or hazy. It should cover the entire thoriated elements, and not be patchy or splotchy.

djacobox372 · Dec 24, 2011

Your lens is radioactive, which yellows the glass over time. Put it under a uv lamp for a week and it will go away.

Dont worry about the radioactvity, just dont sleep with it under your pillow.

usayit · Dec 24, 2011

Yellowing and haze can be two different symptoms from different causes...

Lenses can have haze from either contaminates or fungus residing on the inner elements. This can be common for lenses in the 50s (all brands and models) or a later specimen that was stored in humid conditions (basement for example). There really is no real easy way to clear out the fungus effectively except through a CLA at a repair shop. In some cases, the elements may need to be polished and recoated.

Lenses that have slightly radioactive lenses can turn yellow but in most cases still usable (clear). The well regarded 50mm f/1.4 Takumar is one case example. Some have shown good results clearing the yellow tint with exposure to UV. I use mine as is. For digital, I correct in post and for film it works fine with B&W negative. THey are still Sharp and clear. If you do decide to expose to UV light, I suggest using a UV lamp. If you use sunlight, I would recommend wrapping the lens in foil leaving just an opening for the glass. The idea is to limit the impact of a direct heat source on the lens body.. which some have reported causing problems (inner lubricants etc).

It seems to have a yellow haze from just looking in the rangefinder, something that the rest of them don't have.

Since rangefinder's viewfinder optics are separate from the picture taking optics, you shouldn't see the yellow haze from within the rangefinder. clarify?