canon rfdr finder fade

[djon]

If a Canon P or other rfdr loses zip in the rangefinder dept, can the contrast be brought back easily with a colored gel in the circular rangefinder spot? Like with old Leicas?

Or is the problem more one of mirroring?

If mirroring, who can fix that? I understand mirrors in old Leicas can be re-coated...what about Canons?

I'm asking because I'm pondering a second Canon rfdr... but might go with CV if Canon finders are terminal probs.

 

[back alley]

not expert enough to know the answers you need but i can say i have 2 canon p's and they both have clear bright finders, no problems at all.

joe

 

[jlw]

Things that, in my experience, can dim screwmount Canon rangefinders:

-- Haze on internal optical surfaces: Can be cleaned off; requires top cover disassembly.

-- Loss of silvering on beamsplitter: Probably can be recoated by someone such as John Van Stelten at Focal Point. Likely to be expensive.

-- Deterioration of silvering on finder framelines on models with reflected-frame finders (VI, P): Not much you can do about it. Only affects brightness of framelines, not viewfinder or rangefinder.

You could create more contrast between the rangefinder image and the viewfinder image by putting a colored filter over the RF window, but this is more of a "band-aid" fix than a real solution, IMHO...

 

[djon]

JLW, yes, you seem to be supporting what Gandy says.

I've asked a tech to look at a P with faded framelines and internal haze...he's not optimistic but won't charge me for a pre-purchase inspection...it would be my second P and his work could bring the camera's cost within $100 of CV-price, so maybe I should think along those lines.

 

[John Shriver]

The Canon RF's use a cemented pair of prisms, with partial silver or gold plating on one internal surface. So that silvering isn't subject to atmospheric pollution. But it means you can't just replace it with a new half-silvered mirror, like you can with a screwmount Leica.

Similarly, the moving mirror is a prism, silvered on the diagonal side.

What this does mean is that the exposed surfaces can be safely cleaned. But if any of the silvering is going, you're probably in "no spare parts" land. Altough I havent' asked Sherry Krauter or DAG if they have those parts...

 

[djon]

Happily my "new" P has bright, well-defined lines...

Interesting, I'd guessed atmospheric polution was the old Leica problem...perhaps smokers.

Are prisms interchangable between late Canons? Might argue for acquiring spare bodies with good prisms and bad shutters.

 

[back alley]

congrats on the p!

great cameras.

joe

 

[jlw]

The Canon RF's use a cemented pair of prisms, with partial silver or gold plating on one internal surface. So that silvering isn't subject to atmospheric pollution. But it means you can't just replace it with a new half-silvered mirror, like you can with a screwmount Leica.

I'm just guessing here, but I suspect that someone with the skills of a John Van Stelten (Focal Point) could de-cement the two prism halves and reapply the plating using the same vacuum chamber that he uses to recoat lenses. I've read that Henry Scherer can do this to fix separated Contax prisms, so I'm assuming the same operation is possible on Canons by someone prepared to do it.

As I said in my original post, it wouldn't be cheap!

Incidentally, I've got an original Canon VI promotional booklet that says silver previously had never been used on beamsplitter prisms because it chemically attacks the glass. The booklet claims that Canon found a solution to this problem, allowing them to use silver on the VI's beamsplitter (claimed advantages: greater brightness, more neutral color.) Considering how many Ps and VIs still have pretty good finders nearly 50 years later, I guess there was something in that claim; on the other hand, considering that there's a small but significant minority that DOES have deteriorated prisms, maybe the fix wasn't as 100%-certain as they thought at the time...

 

[John Shriver]

Interesting about Canon's silver claim. The original and replacement beamsplitter mirrors for my screwmount Leica look to be aluminized.

Interestingly, both my Canon IIF and IV-SB2 have the greenish viewfinder with a golden moving image that is typical of gold in the beam-splitter. Not as strong as a Aires Viscount, which has a very obviously gold beam-splitter.