replacement for rangefinder mirror ??

C

chris_zeel

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Aug 6, 2014
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I just got a Neoca 2S, in okay condition, shutter working, focus smooth, optics need some attention.

Importantly, the rangefinder patch was virtually invisible. Only blinding the viewfinder window revealed a small patch from the rangefinder.


I opened up the top of the camera the situation visible in the attachment.

Everything seems in order but the rangefinder mirror is missing/corroded.


How do I fix this? Where to get a mirror? Of should this piece be repolished, resilvered?
 

Attachments

  • neoca_rf.jpg
    neoca_rf.jpg
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Luckily, that's a fully silvered mirror that you've lost, rather than the semi-silvered beamsplitter at the other end. A great place to get optical quality mirror stock is in old Polaroid One Step instant cameras (the ones that squirt the photo out the front below the lens) at thrift stores and flea markets. Each camera has a large front-silvered mirror, 1mm thick, on the 45 degree slanted surface between the lens and the film plane. You should be able to cut the piece you need from one of these and still have enough left over to restore a TLR.
 
Thanks for your advice.

Not sure how soon I will find that camera, but I'll be on the lookout.


Anyone perhaps who did this trick before and has a small piece of mirror to spare?
 
I just opened up a Ricoh 500G that could serve as parts donor, but that one also had a (thick) glass mirror.

I'm also curious if the type of mirror makes a difference.

I would say that it (at least) needs a new calibration.
 
When I made a couple of Newtonian telescopes I found a firm who coated in a vacuum the mirror using aluminum. Less tarnishing.

Don't forget the thickness of the glass you have coated (coating the back) has a bearing on distance and correct (incorrect) for focusing. I believe front coating is the accurate way.
 
Get a dead SLR body at a photo fair or garage sale. Or buy new from Surplus Shed. They have front surface mirrors (possibly thicker than yours) and dichroic mirrors.

Thickness is not that critical. Your effective baseline will change by ~0.7 times thickness difference; if so, your RF, when calibrated to infinity, will be slightly off at minimum focus. Possibly even that can be adjusted.
 
Vintage35 said:
Front silvered? All my cameras (seem?) to have normal mirrors. Is it important?
Click to expand...

Barely any camera ever had rear-silvered mirrors, as these show a offset ghost image (at the usual 45° the reflection from the glass front is offset by more than the glass strength from the rear mirror reflection). Even the brilliant finders on cheap boxes generally use a bit of chromed metal rather than a rear-silvered mirror.
 
As Bill says, astronomical mirrors are aluminised on the front surface to prevent ghost images. It's a little less reflective (maybe 10% less) but much more durable. I used to know a guy in the UK many moons ago (David Hinds) but there are people out there so I expect you could turn one up if need be.
 
Thanks for the responses.

Rick was very kind to send me some spare mirror material he had, so I can hopefully fix the rangefinder soon!
 
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