M4 Trivia.

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planetjoe

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Hi, all.

Recently coming upon maddoc's tempting Classifieds ad, I noticed the suggestion that the M4 bodies with the "barrel-shaped viewfinder mask" are later editions, in which the VF prism is glued with synthetic balsam.

I've been killing myself to find other references to this tidbit, which grabbed my attention in since I'd never heard it before (and I also own such an M4); all I could find thus far is this forum reference mentioning the mask shape. Interestingly, some M2 bodies show up with this feature - perhaps a retrofit?

Anyway, I'm not skeptical - just curious - as well as surprised that other references are hard to find. Can anyone confirm this interesting detail?


Cheers,
--joe.
 
I didn't know it about this either until I stumbled over it over there at photo.net. There was some discussion about the durability of M4 cameras and somebody mentioned that the older M4 might have prism separation (in fact somebody reported that he had this problem with his M4 a couple of years after purchasing new) I also saw photos in one of the threads showing the different shaped eye-piece mask. The older M4s seem to have round masks as do the M2 / M3 have.

Cheers,

maddoc
 
Hi all,
Another data point, my M4 (11800--) has the square mask and separation starting in the lower area.
 
I've got a pair of M4's.... Early one has the rectangular eye piece mask while the later one is rounded. The early one was from a batch of 100 assembled in Canada during the late sixties.

I often use the early M4 with a made in Canada 35mm Summilux, a true Canuck camera, Eh. ;-)

Glenn
 
maddoc said:
The older M4s seem to have round masks as do the M2 / M3 have.

Cheers,

maddoc
Click to expand...

When you say round, what do you mean? My M2 has a rectangular mask while my M4 has the barrel shape.

Ernst
 
Nikon Rangefinder Digital?

Nikon Rangefinder Digital?

🙄 I keep hearing that Nikon will at a point produce a Digit SP type camera. If this were too happen, what lens mounting system do you thing would be used?
 
ernstk said:
When you say round, what do you mean? My M2 has a rectangular mask while my M4 has the barrel shape.

Ernst
Click to expand...

My M3 has a round shape, no rectangular mask being visible when looking from the back- or front- side. My M4 has a barrel-shaped mask like the newer M cameras (M4-P, M6 etc).
 
Here's a photo of the M3 eye piece of mine:

90889588.oLriSlcF.jpg
 
I had two M3 before the one I now have but don't remember if they had a rectangular or round shaped eye piece mask... Can't tell about the M2 since I have never owned / handled one. Maybe that rectangular mask is just missing in my current M3 or one of the frequent undocumented changes during production.
 
Both of my M4's (>1,2xx,xxx) have the barell shape masks and no seperation. I've seen some earlier one's (1,1xx,xxx range) that had the rectangular masks and they all had the "golden droplets" (precursers of seperation) along the prizm when I looked through the front, as did all the M2's I've seen except the M2R's which had the barell shape and no droplets. Hmmm.
 
Wow, lots of answers - thanks for the feedback. I didn't realize tat this variation existed, nor that it would be so hard to corroborate.

I'm chastened now, because upon inspection I realize that my M4 doesn't, in fact, have the barrel-shaped VF mask. I'll have to get back to everyone with the serial#, though.

There's no VF prism decementing yet, although the RF patch itself (yet another cemented prism) has some signs of "crinkles" at its outside periphery. Gotta get it to DAG for a checkup one of these days.

Here is Puts' succinct description of the RF/VF designs in M-bodies; it was some help in understanding where all the parts go. I also recall a hand-drawn explanation in pdf form I saw on the 'net once; it seemed like the kind of thing Dante Stella would do, but I can't seem to find it, now.

The tidbit (mentioned in the first link I posted) about some M2s having this feature is also interesting.

Cheers,
--joe.
 
vrgard said:
Can someone explain what exactly is meant by "barrel shaped mask?" Or a link to where this is explained? I have an M4 in the > 1,2nn,nnn range and would like to know what to look for.

Thanks,
Randy
Click to expand...

A photo is worth 10^3 words...

I don't see much difference using the two versions. You might be able to see the wide frame lines easier with the later one, but wearing glasses negates any advantage.

Glenn
 

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visiondr said:
...what does rangefinder prism separation actually look like? What should I be aware of?
Click to expand...

A canonical description of this problem, and how it happens, is given by CRR Luton on their page. In addition, there's this explanation by Andrew Nemeth (scroll halfway down), although he refers more to the M3 RF system; there's also this RFF thread from a couple weeks ago.

Most folks describe incipient decementing as features around the edge of the viewfinder that look like cracks or bubbly texture; apparently the balsam can degrade with exposure to air, sometimes giving a yellowish cast. Complete separation, of course, would leave the VF dark save for the inner RF patch.

I also believe that decementing can occur in the RF patch optical system (as I believe there is a second cemented prism there), but I don't know of any examples I can point out. Perhaps it's less common - my assumptions might also be wrong.


Cheers,
--joe.
 
visiondr said:
I wonder, what does rangefinder prism separation actually look like? What should I be aware of?
Click to expand...

Ron, here's what mine looks like:
attachment.php
 

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