Low contrast RF on M3 - what's the cause?

[Paul T.]

Dear experts,

The rangefinder patch on an M3, of which I've just taken delivery, seems to be to be very low contrast. I've appended photos below, sorry for the quality, which show the RF patch for the M3, and my CL. As you can see, on the M3 patch the secondary image is barely visible - you can just see the badge on the speaker cabinet, but you can't see the secondary image of the speaker itself, whereas it's clear on the CL RF patch. I have used just one M3 before, and the RF patch seemed infinitely superior to this; likewise, there is no comparison to the M4 which I owned until recently, and was very easy to focus.

So, my question: is the low contrast caused merely by dirt and haze in the finder? Or could there be a more serious cause like oxidation on the prism silvering, or balsam separation? If it's the latter, then I presume I'm looking at around $250 for a rf restoration at crr - who also have a long waiting list - which would be uneconomical with a DS M3 like this one, although in other respects it seems a fine example.

TIA

These photos, poor as they are, give a pretty accurate impression of what you can see thru the viewfinder...

M3 viewfinder

CL viewfinder, for comparison...

 

[Magus]

Post deleted by posters request

 

[Paul T.]

I hope I'm wrong and that there is a not-so-expensive cure for this.

PS. I love your armchair!!!

Best,[/QUOTE]
Thanks, LOL, that poor 70-year old armchair, and its twin, looked quite new until two toddlers decided they made good trampolines...

Re the M3, there does seem to be a lot of sample-to-sample variation... the last one I used, a DS which had sat idle for the 20 years, had a terrific VF which I remember as looking better than my M4. Unfortunately, I'm not experienced enough to know whether this is dirt and haze, or something more serious...

 

[kinoglass]

The RF itself can be the source of the haze, separation of the prims very likely. The frame bright lines assy is also a cause. This is made of two thin glass cemented together using the (in)famous Canada balsam.

However sometimes there is just simply, a removable coat of oil vapours deposited on all optical surfaces of the RF assy and careful cleaning can restore contrast without any major surgery. I can provide such services.

 

[ray_g]

I think the problem may be with the RF. As you can see, although the viewfinder image is a bit hazy, the brightlines are bright but the RF patch is not. The best recourse is to email these photos to CRR or to Sherry or DAG, for an opinion, but I think you may be looking at an expensive repair.

 

[Paul T.]

If the prisms have separated, does this generally require resilvering of the mirror?

Incidentally, of people who've handled loads of M3s, how common is this problem?

 

[colyn]

If the prisms have separated, does this generally require resilvering of the mirror?

Incidentally, of people who've handled loads of M3s, how common is this problem?

A good repairman won't just re-cement the prism. He will also re-silver the mirror which is recommended otherwise your next repair would be re-silvering.

I currently have 2 M2's, 4 M3's, and a M4 and have never seen this with any of them. I just re-cemented the prism blocks of a Visoflex right angle finder though.