All Fogged Up – A Repair Tale

If you work and play with a camera in less than ideal conditions, then you should learn to do a basic check and clean. A while back I had to go a bit beyond that with my Mamiya Prism Finder. So here is the deal, instead of a semi-heroic tale of camera usage that wrecked havoc on that fine piece of optical construction, it was only sitting in my bag this time. The eyepiece of the viewfinder was sticking out of my shoulder bag and it got a bit wet due to some odd raindrops. Usually, this isn’t a problem, a quick wipe with a cloth and it’s all okay. But later that day, I noticed that the viewfinder fogged up. Sure, things like this happen, all I got to do is let it air out. Not today though! It just wouldn’t clear up and after closer inspection, I could see some fluids on the inside of the prism housing.

So, I did the only sensible thing that I could think of; take it apart and see what happens. First of all, I had to open up the housing. The top cover was fixed by four screws and once those were out, it could be wiggled free. Yes, wiggled, since it was stuck at the one point (some glue might have been introduced on my behalf to keep the rubber eyepiece on). Once gone, it revealed the prism inside. Keep in mind, this thing weighs about a kilo and as I look at it, that’s about ninety-five percent from the glass.



But that was expected. The one thing that  I keep wondering about, is what that punctured plastic plate is in front. Yes, it is used to add some extra rigidity, but there are less odd ways to do that. My best guess is, that this part is also used as the baseboard for the electronics in the same prism finder type that does have a light meter. If somebody knows, please confirm this.


Anyhow, this still didn’t help that much with the moisture problem. Even though it looks pretty awesome like this, we have to dig deeper to solve this problem. The prism was secured at three points (if you count the front construction as one) and lay on a couple of foam pads. A couple of quick turns with an extended screwdriver and the prism came free. It’s absolutely a jewel. It is actually made up out of two prisms, with the lower part fully blacked out on the sides. I find so much joy in the knowledge that something this futuristic looking is hidden inside that bulky plastic housing. Stuff like this is why I love taking things apart.



Back to the case -hehe- at hand. Once the prism was removed, I could finally begin with the damage assessment. A decent amount of water has seeped in and left a foggy residue all over the glass surfaces. It has been a couple of hours since we got home and that there was still some moisture inside, so I’m quite surprised about this. I have to remember to add a better water seal to this thing. It was quite easy to dry everything up from this point. The next challenge was to clean the prism itself. It took me a good ten minutes to get the underside nice and clear again. For the rest, it was getting the glass surfaces dust and streak free. When I originally got this viewfinder, it had a fair amount of dust stuck to the eyepiece, so I took care of it too.














The reason why I find it important to solve issues like this so fast has two main reasons. First, it bothers me that my camera is not ready to grab and shoot. Second, stuff like this can cause serious (optical) problems. The fact that it was so hard to get the prism clean, even just after such a short time period, is a good indicator how sensitive these elements are to certain contaminations. Now think about this word; ‘mold’. If that starts to form on your glass, then you are not a happy puppy anymore. With touch-ups like this, you can keep your gear going without having to go to a repair center. Especially if it’s for older gear. Now, my prism finder is dust free and cleaner than when I got it in the first place. If possible, then do try and find the manual of your camera or piece of gear, or even better a repair manual. A great source that I have relied on many times for this is They have a huge archive of old manuals for photographic equipment. The more information you have about the things you work with, the better.


One final advice for stuff home repairs; don’t go screwing around blindly, make an estimation what is in your skill range. For example, I won’t change a matte glass in a DSLR or mess too much with electronics. Why? Because I am either not comfortable enough with the process (yet) or not skilled/equipped enough to do the job.

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