Got Haze?

My RB-67 Got Haze.

Earlier this year I pulled my old RB-67 out to admire it and noticed that the 127mm lens had developed a nasty case of the haze.   While doing some internet research, I found that there is a guy on Youtube who makes disassembling Mamiya lenses look easy.  After collecting a few needed tools, I took the lens apart to find that the haze was between elements that were glued together and mounted in a metal collar.  In fact, there were two such lens pairs in the lens, one in front of the shutter and one behind.  Both were fogged.

My first solution was to buy a used lens on ebay, upgrading from my Mamiya-Sekor C lens to the better K/L version.  The one I bought was specifically described with words like “Near Mint” and “no haze”.  Unfortunately, it did have haze, so I returned it, very much discouraged from trying to find a replacement on ebay.

My next solution was to send the lens to a repair center that told me they could separate cemented elements and re-glue them.  But, when I sent them the lens, they told me they couldn’t do it because of the way the elements were sealed in the metal collar.

Enter the Wizard.

So, I turned to the Photrio forums where a poster named Charles Monday, (aka shutterfinger) suggested that heating the cemented elements in an oven would very likely clear the haze by softening the Canada balsam cement between the elements.  I was skeptical, but eventually I decided to give it a shot.

It worked.

I don’t mean it worked a little bit.  I mean, I had to struggle to find any remnants of haze.  I decided to create a short blog post to tell the story because, in a search of ebay listings for about twenty 127mm Mamiya lenses, all but two of them were described as having some haze.  I’m sure this condition affects other lens brands and I’m sure this remedy will be equally applicable to other old lenses, but I only have experience with my one RB-67 lens and I wanted to do my part to spread the word to other RB/RZ-67 owners that this really works to substantially reduce haze between cemented elements.  But, please see the disclaimer at the end of this article.

The procedure.

The recommended procedure consists of heating the glued pair of elements in an ordinary kitchen oven at 325F (163C) for 30 minutes, letting it cool down slowly on its own, and then repeating the procedure twice more.  Then wait for a few days to see if the lens clears.  It it doesn’t, you should repeat the process again.

My Experience.

So, I basically followed the procedure exactly.  I used a thermocouple at the lens position in the oven to monitor the temperature just out of curiosity.  I preheated the oven to 325F (183C), placed the lens pair, complete with the metal collar, in a small shallow metal cookie pan and placed the pan in the middle of the oven’s center rack.  The thermocouple indicated an initial temp after preheat of 377F, but after that it varied between 309F (154C) and 352F (178C).  Half an hour later, I turned off the heat and let it cool for several hours.  After two heat cycles, the lens was still cloudy, but after the third cycle, the lens had cleared.  The milky haze was gone.

The next day I repeated the procedure with the front pair of cemented elements and the milky haze disappeared after the first cycle.  Why it cleared quicker, I don’t know.  Maybe it had less fog or maybe the oven was a little hotter for some reason.  In any case, for this pair I was astute enough to take before and after pictures (scroll down).

The Results.

The bottom line is that this simple process has the ability to substantially reduce haze without doing any perceptible damage to the coating or the mechanical mounting.  Is it a miracle cure?  No, although at first I thought I thought it was.  The haze was originally pretty bad on my lens and there remains, on the rear pair of elements, a slight bluish cast to the lens if you shine an LED flashlight through it.  That residual haze is enough to lower the contrast of the resulting negatives.  The front elements cleared almost completely.  It seems likely that the less severe the haze, the less residual haze there will be after the treatment.

This may not be the end of the story.  The residual haze may continue to clear after the heat treatment.  I plan to let it sit for some weeks or months and then reevaluate whether to subject it to a longer heat cycle or retreat it at a higher temp.


Rear Cemented Element Pair Module

Front Cemented Element Pair Module

Front Pair BEFORE Treatment

Front Pair AFTER Treatment

Front Pair BEFORE Treatment

Front Pair AFTER Treatment

The Inevitable Disclaimer

Don’t do this to a lens you can’t afford to destroy.  I exhausted other avenues of repair before doing this, so I considered this an option of last resort.  Having now done it, I think the risk is pretty low, but not zero.  Just because a few people made it across the mine field doesn’t mean you will.  Be careful not to subject the lens to sharp temperature changes by placing it directly on a hot surface.

Note that other forms of lens cement will probably not respond well to this technique, but decades old lenses that use Canada balsam are fair game.


See the entire Photrio thread here.

5 thoughts on “Got Haze?

  1. Hello,

    I’m experiencing this problem with my 127mm. I would like to know if your problem has reappeared ?

  2. Hello Reda and thanks for your question.

    While I did check the lens several months ago (probably more than a year), I did not see any improvement. I mention that because there has been some mention that the lens will continue to improve over time after the heat treatment. In fact, as I remember, it may even have looked a little worse.

    In any case, in response to your question, I looked at the lens again today and noticed that, while the haze hasn’t cleared, it now has taken on a donut shaped appearance. Around the edges of the lens it looks quite clear. The center is also less hazy. It may just be that the haze has gotten worse in a concentric ring, but the lack of any apparent haze around the edges makes me wonder if I gave up too soon. To my mind, the haze has ruined the lens, so I have nothing to loose from doing more vigorous heat treatments in the oven. I removed the rear lens group and it is once again sitting in the oven at 325F. I am planning to leave it in there longer this time and I may try higher temperatures.

    The front lens group (which had less haze than the rear group) is still crystal clear with no sign of any haze returning after I treated it originally. That should be encouraging for anyone with a lens with a low level of haze.

    I am not expecting much success, but I will post the results of my current experiments as an additional comment so feel free to check back. If you don’t see anything here within a week or two, feel free to contact me about it.


  3. This is a follow-up to my comment of yesterday above.

    I kept the rear lens group in the oven for an hour at 325F and then turned off the heat and allowed the lens to cool in the oven. The result was that the haze from the the cemented lenses again uniformly covered the entire diameter of the lens. The clear area around the circumference as well as the center are now just as hazy as ever.

    I reinstalled the rear lens group back into the lens assembly and will inspect it again after a month or two.

    It is a pity that there is no sure fix for the deterioration of Canada balsam cement for lens pairs like this. It seems fairly likely that this kind of haze will eventually render all lenses that use it as useless. That doesn’t bode well for Mamiya lenses. Even MINT+++++++++++ Mamiya lenses sold by Japanese sellers on ebay often indicate in the description that the lenses have haze.


  4. Hi, Reda.

    Welcome back. I assume you haven’t been able to find any other solutions to the haze on your lens.

    My 127mm lens shows no sign of clearing since my last comment. If anything, it’s worse than ever. I think the only solution is to just get a new lens. I’ve been watching for used 90mm and 127mm KL lenses. I’d be happy with either focal length. The KL lenses are newer and should be less likely to have haze. The only thing holding me up is that I just spent a lot of money getting a Hasselblad system, so I’m not quite ready to spend several hundred dollars more on a Mamiya lens. I will get one eventually, though. Not having a “normal” lens for an otherwise complete RB-67 Pro-S system bothers me.


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