Does the Bessa R3A rf patch move?

[thmk]

Hi all,

today I got my Bessa R3A back from rangefinder adjustment just to see that the rangefinder patch is now tilted to the left side. So I'll have to send the camera straight back to the service. What also makes me wonder is that the patch does not move with the framelines when adjusting the distance. That is not the case with the R2, R and the Leica M2.
My question is now if anyone with a R3A could just check if the patch really does not move. If it should move the service really did a lousy job and I will have to tell them.

Cheers
Thomas-Michael

 

[jlw]

I just checked mine, and the patch on the R3a definitely doesn't move. It isn't supposed to. (Actually, IIRC, it doesn't move on the previous Rs, either -- I think its lack of motion is just more evident on the R3a because of its higher finder magnification.)

If you ever open one of these cameras and look at the internal rangefinder mechanism, you'll see that the framelines are projected into the viewfinder by a thin slotted mask (the slots form the lines when illuminated by the frosted window on the camera front) and that the lines are moved to compensate for parallax by a mechanism that makes this mask slide diagonally.

The rectangular borders of the rangefinder patch are created by a different mask located elsewhere in the RF/VF optical system, and there's no mechanism provided to move this mask in step with the frameline mask. (This second mask is probably what got tilted when you had your camera serviced; should be fairly easy for them to put right.)

 

[thmk]

Ok, many thanks for the fast check. So the service just have to check why the patch is tilted. I did not keep an eye on the rf patch movement until today. Just saw that the patch definitely does move with the framelines in the R, R2 and M2 after a friend asked me why it does not move like in his R2.

Cheers
Thomas-Michael

 

[jlw]

Interesting. I'll have to find a diagram of those RFs and see how they do that.

Here are a couple of illustrations I scanned from a Japanese book (it's about the Epson R-D 1, which is based on the R3a, so I assume they have the same rangefinder mechanism. I added the labels in red.)

The first one is a photo of the rangefinder mechanism from the front side; you can see the slotted mask that creates the framelines. It moves diagonally on the small pins visible in the corners. The shiny chrome piece you see below the mask is what makes it move -- you'll notice that it bears against a pin in the RF pivot on the right side, and there's a tiny cam cut into it on the left side. This cam bears against the pin in the lower left corner of the mask, and makes it move diagonally as the chrome piece slides sideways. You also can see a hairspring at the upper right corner of the mask -- this provides pressure to hold the pin against the cam.

Notice that the center of this mask is solid except for a couple of tiny holes, which I assume are for aligning it. The rectangle that forms the RF patch is not in this location, so it would not be able to follow the movement of the mask.

The second illustration is a simplified drawing of the RF optics. The RF patch mask is between the viewfinder and rangefinder sections. Components are very tightly packed in this area, and I can see how it might be easy to disturb this slightly when adjusting the rangefinder.

Note that the tilted patch is just a nuisance; it shouldn't affect RF accuracy, so there would be no risk in using your camera until it was convenient to send it back for adjustment.

 

[ZeissFan]

If the patch is tilted, it's because the mask is rotated slightly within its mount, I believe.

 

[einolu]

I have to move my eye around to always see the rf patch on my R (as in, it sometimes disappears when you change focus), is this what you are talking about thmk? I find it annoying, do you have to do the same thing with an R3a?

 

[thmk]

I am just talking about that the patch does move in line with the framelines to be in the center of the marked frame. In the R3A it will be off the center when changing focus.