Leica IIIf rangefinder spot dimness

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Silme Ea

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Hello RFFers!
I know that it is a common problem with rangefinder spot dimness in Leica IIIc/f, and I know thanks to reading through this great forum that this issue could be corrected by replacing the rangefinder mirror, but what is exactly "dim" and "bright"?
I've recently bought a IIIf and it went through a CLA already. Being alert of the rangefinder dimness issue, I asked the workman whether should the mirror be replaced. I got an answer that he cleaned all the grease inside the viewfinder and rangefinder, and there's no need to replace the mirror. He is a wise man, I can trust him in this matters, though on the other hand I'm not entirely satisfied with the rangefinder perfomance. I can focus just well, but it takes a while, because the spot itself is barely visible, and the double image is clearly dimmer. I did a comparison with a Zorki-1, and IMO he wins it.
Here's the photos (quality is lousy grace à my cellphone):

Leica IIIf


Zorki-1

So, should I listen to my workman and stick with it (maybe he just didn't want to bother), or replace it myself (I fixed only one camera in my life, and it wasn't Leica or similiar)? And would a new mirror really give big difference? Perhaps someone could photograph it, or just tell me that I should run for my screwdriver set and replace it immediatly? 🙂
 
The Zorki-1 you find now will likely show a brighter and snappier rf spot than just about any Leica IIIf (or IIIc or even IIIg). The Soviets used a far superior silvering material which resists aging and tarnishing better than what Leitz used.

If you can live with the 'faint' (relatively speaking) spot on the IIIf, leave it be. Replacing it may just lead to more trouble than it's worth. If you really want the half-mirror replaced, at least have it done professionally.
 
It's not the mirror, it's desilvering of the beamsplitter that combines the mobile RF image with the direct vision image. It is a common affliction for cameras this old.

Don Goldberg has replaced the beamsplitters in my IIF and IIIG. Now they are almost as sharp and contrasty as the view from my M7. I say almost, because the M7 has anti-reflection coatings and polarization to enhance the viewfinder/RF contrast.

You have answered your own question. If you can't use the camera easily, then the beamsplitter needs to be changed. I think DAG charged me a bit over $125 to do this, but it was part of a general overhaul of the cameras. It WILL considerably improve your enjoyment of using the camera.

PS: A lot of techs don't have these parts, hence they may discourage you from doing anything.
 
I've had a look at my collection of LTMs and your IIIf does look dimmer than my IIf and IIIf RD but is about the same as my IIIf BD. My Zorki 1 and Fed 1 are not as bright as yours. My IIIf BD is my shooter despite being a bit dimmer.

It all boils down to usability, if you can't work with the dimmer RF then you may be forced into getting the mirror replaced but at a cost
 
Thanks for all your answers! Not that I can't completely stand it like it is, though the possibility to make it better itches me 🙂 In fact, I have a new spare mirror (japanese one) lying in my desk's drawer, so it's down to whether it costs the fuss of replacing 🙂 Maybe someone else have it done with his/her camera and could share the experience?
 
Robert Lai said:
It's not the mirror, it's desilvering of the beamsplitter
Click to expand...

Pardon me, but as far as I know the only "beamsplitting" part of a IIIf rangefinder is the mirror itself, isn't it? Or maybe we're calling the same thing different names?
14363.jpg
 
Number 3 in your diagram is what I'm referring to as the "beamsplitter". That's DAG's term, not mine. It allows 50% of the light from the RF path to be merged with the 50% transmission from the direct view. When it desilvers, you get less and less of the RF patch visible.

#6 is also a mirror which is mobile, and performs the triangulation for the rangefinder.
 
Yes it does look rather dim, a very common problem with old screw-mount Leicas. If you are reasonably handy and feeling a bit brave, the replacement of the semi-silvered mirror, part #3 in the diagram above, is really quite a simple fix, and the part can be found for $10 on ebay.

http://www.ebay.com/itm/Beam-split-...992115253?pt=Film_Cameras&hash=item19d7a54635

I have replaced the mirrors on several of these cameras using this part. All you need to do is to take the top off the camera, which is a bit fiddly, but not difficult. There is a square plug, about 7mm, on the end of the rangefinder housing, through which the old mirror is removed. It is typically not glued in very hard, but it might be necessary to pry on the edge of it a bit through the RF window with a wooden tool (toothpick or skewer) to get it out. Clean the mounting surface very carefully, as it is imperative that the new mirror goes in straight. When fitting the new mirror, remember the silvered surface faces the rear of the camera. Fix it in place by putting a very small amount of glue on the rails that support the mirror. Press it in place using your wooden tool, and let the glue dry before going any further. It will be necessary to re-do the vertical and horizontal RF adjustments after reassembling the camera. I believe there are many strings on RFF showing the method of doing that.

Cheers,
Dez
 
I'm sure you already know this, but just in case -- have you tried focusing the rangefinder image with the lever beneath the rewind knob? The IIIf is my favorite for shooting in dim light because the image is magnified. The rangefinder is more than bright enough for me in ordinary light. My inherited IIIf has gone through three very different climates on three different continents without the rangefinder and viewfinder ever having been cleaned.
 
Robert Lai said:
Number 3 in your diagram is what I'm referring to as the "beamsplitter". That's DAG's term, not mine. It allows 50% of the light from the RF path to be merged with the 50% transmission from the direct view. When it desilvers, you get less and less of the RF patch visible.

#6 is also a mirror which is mobile, and performs the triangulation for the rangefinder.
Click to expand...

The beam splitter is really a 50T/50R (ideally) mirror. Half silvered, so only half of the light is reflected and half is transmitted. Both terms are acceptable, (half) mirror or beamsplitter. The term 'desilvers' is used- and mirrors are indeed silvered.

No.6 part in the diagram is really a prism. Partly also silvered, but not conveniently a true mirror. 🙂
 
To the OP: replacing the mirror is quite easy, if you know your way around small precision machines.

Assuming that you can breeze through the process of disassembling the top, and removing the mirror mount from the RF assembly, the next hurdle is how to remove the mirror cleanly and mount the replacement properly.

The replacement mirror must be mounted absolutely flat. Remnants of the old cement must be thoroughly removed. The new mirror should sit squarely on the mount. A slight tilt or slant- as can be caused by old bits of cement- will prevent the RF patch images from aligning horizontally.
 
ZorkiKat said:
To the OP: replacing the mirror is quite easy, if you know your way around small precision machines. . . .
The replacement mirror must be mounted absolutely flat. Remnants of the old cement must be thoroughly removed. The new mirror should sit squarely on the mount. A slight tilt or slant- as can be caused by old bits of cement- will prevent the RF patch images from aligning horizontally.
Click to expand...

I shudder the thought of trying something like this. If the OP has some experience, he could try. 😱 My solution was to buy a IIIf from Youxin Ye. I asked him to put the camera in excellent user condition and in addition to the usual CLA, he put in a new beam splitter mgf. in Japan before mailing the camera to me. Here are two relevant links from a RFF thread a year ago:
http://www.rangefinderforum.com/forums/showpost.php?p=1982364&postcount=3
http://www.rangefinderforum.com/forums/showpost.php?p=1982373&postcount=4
If you are not in the USA or do not have an American address, he may not do business with you, but you could contact him and see.
 
summar said:
I'm sure you already know this, but just in case -- have you tried focusing the rangefinder image with the lever beneath the rewind knob? The IIIf is my favorite for shooting in dim light because the image is magnified. The rangefinder is more than bright enough for me in ordinary light. My inherited IIIf has gone through three very different climates on three different continents without the rangefinder and viewfinder ever having been cleaned.
Click to expand...

Yes, I've surely tried it 🙂, but thanks for trying to help. I suppose you have a red dial IIIf? I've heard they are less prone to deterioration problem.
 
ZorkiKat said:
To the OP: replacing the mirror is quite easy, if you know your way around small precision machines.

Assuming that you can breeze through the process of disassembling the top, and removing the mirror mount from the RF assembly, the next hurdle is how to remove the mirror cleanly and mount the replacement properly.

The replacement mirror must be mounted absolutely flat. Remnants of the old cement must be thoroughly removed. The new mirror should sit squarely on the mount. A slight tilt or slant- as can be caused by old bits of cement- will prevent the RF patch images from aligning horizontally.
Click to expand...

I've recently fixed a FED Micron, but that's my only experience. On the other hand, I have two broken Zenits to hone my skill, so I'm more and more inclined to change the mirror myself. Two questions - would I need to readjust anything except the rangefinder itself and would some cyanoacrylate be good to cement new mirror?
 
traveler_101 said:
I shudder the thought of trying something like this. If the OP has some experience, he could try. 😱 My solution was to buy a IIIf from Youxin Ye. I asked him to put the camera in excellent user condition and in addition to the usual CLA, he put in a new beam splitter mgf. in Japan before mailing the camera to me. Here are two relevant links from a RFF thread a year ago:
http://www.rangefinderforum.com/forums/showpost.php?p=1982364&postcount=3
http://www.rangefinderforum.com/forums/showpost.php?p=1982373&postcount=4
If you are not in the USA or do not have an American address, he may not do business with you, but you could contact him and see.
Click to expand...

Yeah, thanks, I know Youxin, he's a great guy. Although I'm not from the USA, I've brought a Summitar from him and all went well. I considered to send my camera to him, but postage costs dearly, and CLA itself is not too cheap for me too. I'm already running out of my student's budget 🙂 I should had had my Leica from him, I know. Maybe if I ever buy a M... 🙂
 
Dez said:
Yes it does look rather dim, a very common problem with old screw-mount Leicas. If you are reasonably handy and feeling a bit brave, the replacement of the semi-silvered mirror, part #3 in the diagram above, is really quite a simple fix, and the part can be found for $10 on ebay.

http://www.ebay.com/itm/Beam-split-...992115253?pt=Film_Cameras&hash=item19d7a54635

I have replaced the mirrors on several of these cameras using this part. All you need to do is to take the top off the camera, which is a bit fiddly, but not difficult. There is a square plug, about 7mm, on the end of the rangefinder housing, through which the old mirror is removed. It is typically not glued in very hard, but it might be necessary to pry on the edge of it a bit through the RF window with a wooden tool (toothpick or skewer) to get it out. Clean the mounting surface very carefully, as it is imperative that the new mirror goes in straight. When fitting the new mirror, remember the silvered surface faces the rear of the camera. Fix it in place by putting a very small amount of glue on the rails that support the mirror. Press it in place using your wooden tool, and let the glue dry before going any further. It will be necessary to re-do the vertical and horizontal RF adjustments after reassembling the camera. I believe there are many strings on RFF showing the method of doing that.

Cheers,
Dez
Click to expand...

Thanks for encouraging me, I think I would try it 🙂
 
Silme Ea said:
I've recently fixed a FED Micron, but that's my only experience. On the other hand, I have two broken Zenits to hone my skill, so I'm more and more inclined to change the mirror myself. Two questions - would I need to readjust anything except the rangefinder itself and would some cyanoacrylate be good to cement new mirror?
Click to expand...

There are some instructions to be found online, with illustrations, which describe how mirror replacement is done. From these descriptions, you can gauge whether you will want to (or can) do it.

Cyanoacrylate is a good adhesive, but not best to use. It can set too quickly which will not allow resetting of the glass in case the installation is not correct. Shellac based cement is better. Or the celluloid-based cements recommended in some of the repair manuals. The latter actually calls for some old film base which is dissolved in acetone or similar solvent.
 
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