Lens Plane : Film Plane

Rangefinder Optics...Mirrors

Rangefinder Optics...Mirrors

Anyone re-silver old rangefinder mirror...comments?
 
for re-silvering a mirror you need a friend in a thin film deposition lab (e.g. at a university, where rules are relaxed) where he could clamp in your little piece of glass (ex-mirror) next to his sample, and deposit a few nanometers of some metal as a byproduct for his research.

You could go for a variety of materials this way besides silver - titanium, gold, platinum, tantallum, nickel are used often, more often than silver (and are corrosion resistant).

I've been in this field before, but not anymore.
 
well, now i know coz you told me. :D
I have no experience with that method.
I only write about what I know.
 
Was just passing it along in case, as I just found it...

Anyone tell me how one makes the lens plane parallel to film plane?
 
I'm not sure what you're asking. The stops that lock the front standard into place are supposed to hold it parallel to the film plane. If they are damaged or deformed, then there could be an issue, but otherwise it should be OK.

Now, if you're trying to repair a damaged camera, you need to measure the depth from several points around the perimeter of the shutter mounting plate to the film plane with a micrometer. Very slight adjustments might be possible with tweaking the metal, but the better, more precise solution is to shim the mount as needed to level the shutter/lens and the film plane.
 
BobBill said:
Was just passing it along in case, as I just found it...

Anyone tell me how one makes the lens plane parallel to film plane?
Click to expand...
Do you have a particular model of folder in mind ? If so, a (link to) a picture identifying the design of the part(s) of the hardware which is/are in question would help to make any responses most applicable.

A couple of questions occur immediately, for example :

Is the lens standard firmly located when deployed, whether to a fixed position or on a track as the case might be ?

Is there sufficient access to the film plane to bring some sort of reference surface or instrument to it ?

PS Answer drafted before I saw O2Pilot's response above; apologies for some implicit duplication, but I thought I'd pose the questions anyway :)
 
The only way to accurately measure shutter plate to film plane distance is to remove the shutter. Use a plunge micrometer from the front of the camera.
 
We should probably ask the OP why they need to know. If we don't know what exactly the problem is they're having it's going to be difficult to give them a useful answer.

To the OP, it helps us help you if you are more specific with your questions.

Thanks!
 
1. Film and lens are kept in parallel by wobble. More seriously, they have quite a variety of scissor/pantograph mechanics. Some folders are better designed than others - but all can be worn out and will wobble or lose their alignment. Folders with tilting lens tend to be more prone to wear and wobble than permanently parallel ones.

2. Re-silvering old mirrors is more of an effort than simply replacing them. Getting the old bit of glass clean and re-polishing it is not easy, and a complimentary coating may not have the properties you need. Industrial strength hard-coated surface mirrors are cheap (I paid $20 for a tile I can cut dozens of RF mirrors from), and even a bit of high precision 50/50 beam splitter will cost $50 or less.
 
If the thickness of the mirror does not matter or can be compensated you could check obsolete or dead (analogue) SLRs and cut their mirror to size. You become a hero in rangefinder land for that act.

Some time ago I did bring a folder lens more or less parallel again to the film frame. I made a rough job of it to be honest. Using a hammer, anvil, etc to expand the metal parts that lock the folder mechanism. They were worn so the lens wobbled. Then small files to get the right correction. I used a small spirit level to create first a correct level for the filmgate to rest on and then checked the level of the lens rim. The method was good enough in my case (film check of a stone wall with a small mirror in the center, see below) but sure there will comments on this method.

In reprography (old Polaroid MP3 stand) + a digital reflex I used a small round surface mirror on the board to tweak the camera mounting that the camera is plane in both directions and stays plane + centered when it is moved up and downwards. Focusing on the mirror and then focusing on the cameralens through the reflection of the mirror. Sensor image displayed on a Nexus 7. Turn the mirror if you are not sure whether it is plane. Probably an old trick in reprography.

A similar method for a folder could be a mirror that covers and is level on the filmgate and has a small hole in the center with a diffuse LED light behind it. The straight light path and the inside lens rim reflection image should be centered if projected in a dark room and on a more or less parallel wall. Just an idea, never done it. Be aware that the lens may be shifted versus the center of the filmgate but still be correctly parallel to the filmplane. The mirror should have some play to shift to what the lens considers the center.

There must be someone who used an old DVD laser for a job like that and wrote a web page on the topic.

Edit: maybe this .... http://www.largeformatphotography.info/forum/archive/index.php/t-16259.html

Ernst Dinkla
 
I picked up a pristine Konica Pearl 645. But, when looking at the open camera from the top, the lens was canted and further inspection revealed no marks etc that would indicate the machine suffered a blow etc.

I concluded the mechanism was to blame and thought maybe it was made that way. I am sorry but I do not have a picture and send it off for inspection and repair, if needed.

Still, the idea recurred to me and am sure variations in assembly and parts have them different. Just wondering out loud.

The idea of using the mirror from drawer-bound old reflex camera is excellent idea.

I have a Certo that suffers a clouded mirror/rangefinder and was wondering if someone might have messed with theirs.

As I noted, there are some kits to fix larger mirrors and some other data on-line on the topic. I do not have the time now, but plan to fiddle with the camera later in the year.

Appreciate the comments.
 
Someone, I think on RFF (maybe sevo) once mentioned that the struts becoming mis-aligned will sometimes cause a lens to go out of alignment.
 
I do not have the tools to tear into a fine instrument like an old folder, so I gave up and sent it off to a fellow in Menomonie, WI, Carol (Futot) recommended.

Nippon-made camera, like my Mamiya-6. Not too many mess with them, as I can tell...if he dos well, will send the Mamiya in for a CLA...shutter is sluggis sometimes on slow.

I would fool with it, but like I said, no precision tools and little time now crafting sailboat. Will see what happens.
 
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