mooge
Well-known
Canon 7 - Rangefinder cleaning, alignment and stuff
Eugene Lee
v1 17 Sept 2017
1. Introduction
Notes on Canon 7 rangefinder assembly: removal, cleaning, alignment and construction.
Not a step-by-step guide, because I'm lazy and that actually takes time.
2. Disassembly
The top cover needs to be removed, but not the body shell.
The only trick here is the shutter speed dial. Set it to X and ASA 400, remove the long screw at the 6 o'clock position and loosen the other set screws a couple of turns. Don't remove the set small set screws because they are tiny and you won't want to lose them. At other ASA settings the set screws may be covered by the ASA dial underneath. Make note of the position of the light meter display before removing the ASA dial.
Figure 1: Top cover removed
Next, remove the rangefinder assembly. It's held in with three screws (two left of the main beamsplitter, and one by the rangefinder arm), but its removal is blocked by bits of the meter. Remove the meter scale and the background piece, and unscrew one of the screws for the galvanometer and swing the galvanometer aside. Push in the rangefinder roller and pull the rangefinder assembly up and around the bits of the shutter that are over the RF mirror.
Figure 2: RF assembly removed, light meter galvanometer moved aside
I have no idea how the prisms are held in place. Glue? Glass magnets? Centrifugal force? Whatever. I used the trivial approach and left all of the major optical components in place, with the exception of the frame lines mask. It comes off with two screws at the base of the mask assembly. Mine had washers underneath, one under each screw (presumably important). The lens nearest to the eyepiece also comes off easily, with one screw.
3. Cleaning
So this finder had lots of fungus and a bit of haze. To remove the fungus, I use my usual secret weapon: a bit of moisture and foul stench from my breath, and a cotton swab or piece of toilet paper wrapped around a screwdriver or whatever. With luck, the fungus hasn't etched the glass and will come off easily. This time we were lucky.
Figure 3: Fungus on framelines prism
Figure 4: Fungus removed!
The space between the beamsplitters can be accessed with a small cotton swab thing, or something like that. You'll have to remove a light shield and remember to glue it back later.
Figure 5: Cleaning between the beamsplitters
4. Reassembly
The only hangup I had was in getting the framelines moving. There's what looks like a screw on the lever C9312, but it's riveted in the back. I thought it was an eccentric to adjust the framelines but it was hard to turn. And then the framelines would stick when the rangefinder cam was pressed. That screw thing is actually just a slotted cylinder, the slot being there to adjust the diameter of the cylinder such that there is no slop as the framelines mask translates for parallax correction - if slop is there, then the frame lines will change as the mask moves. So yeah, it looks like a screw but don't turn it.
Actually I got hung up on a couple of things.
The shutter button is not symmetric - one of the slots is deeper than the other. The deeper slot goes where the rectangle thing is on the piece underneath, otherwise the A-R ring will jam.
And then when I was doing the final checks after assembling the camera, I noticed the vertical alignment was off. So I tried to fix it through the access hole since the top cover was on. If the shutter is set to 15 or 30, the vertical alignment eccentric is blocked by a lever. And even with that out of the way I found it difficult to find the eccentric - and eventually I got the screwdriver between the eccentric and the RF mirror, and broke the mirror free from the metal. A classic move - break the camera during the final checks.
5. Rangefinder and frame lines alignment
Once I had stopped swearing and glued the mirror back on, the horizontal alignment was way off. Underneath some anti-reflective material near the mirror are two screws, labeled S 1528 in the manual. One of them wouldn't come loose, but the other did (the RF was in place at this point, and I was trying to use the screwdriver around stuff) and with the one closer to the eyepiece loose you can pivot the bracket that holds the mirror around a bit. Use this to get your horizontal alignment within the correct range.
Screw C 2419 is the fine adjustment of the horizontal alignment. For gain adjustment (if infinity is good but 1m isn't), you'll need to make a tool to rotate a cam underneath the RF roller - a 6mm spanner that's 0.030" or something thick, really thin. I never bothered adjusting this. Tightening the screw on the RF roller didn't seem to be good enough to turn the cam.
All of the rangefinder adjustment points are accessible without removing the top cover; the vertical adjustment and fine horizontal adjustment are under screws.
6. Optical diagram
There doesn't seem to be the optical diagram for the Canon 7 viewfinder on the internet, so here is my take on it; from the repair manual drawings and what I can see with my finder partially disassembled. So you're warned, it's correct as far as I can tell, but I could be wrong.
Figure 6: Canon 7RF/VF optical diagram
Figure 7: Front and bottom views
Figure 8: Front and back views
Figure 9: RF and framelines beamsplitters
Figure 10: Framelines assembly components.
Figure 11: Framelines mask
Figure 12: Framelines mask, reverse (side facing aft)
Figure 13: Exploded diagram of RF/VF from repair manual
The interesting thing about the Canon 7 viewfinder is that there are two beamsplitters. One for the rangefinder, with just the centre area semi-silvered; and one larger beamsplitter for the frame lines. This explains why the rangefinder spot does not move with the frame lines as in a Leica; the rangefinder image does not pass through the framelines mask. The frame lines assembly is quite complicated since it has four settings (35/50/85+100/135), and changes frames by having a mask translate horizontally. The rangefinder on the other hand is as simple as it can be, with only a moving mirror. An interesting approach to making a simple, but quite good, rangefinder (I wonder if it's any cheaper than a Leica-style finder though).
7. References
Canon 7 repair manual
Hans Kerensky's Canon 7 notes
Eugene Lee
v1 17 Sept 2017
1. Introduction
Notes on Canon 7 rangefinder assembly: removal, cleaning, alignment and construction.
Not a step-by-step guide, because I'm lazy and that actually takes time.
2. Disassembly
The top cover needs to be removed, but not the body shell.
The only trick here is the shutter speed dial. Set it to X and ASA 400, remove the long screw at the 6 o'clock position and loosen the other set screws a couple of turns. Don't remove the set small set screws because they are tiny and you won't want to lose them. At other ASA settings the set screws may be covered by the ASA dial underneath. Make note of the position of the light meter display before removing the ASA dial.
Figure 1: Top cover removed
Next, remove the rangefinder assembly. It's held in with three screws (two left of the main beamsplitter, and one by the rangefinder arm), but its removal is blocked by bits of the meter. Remove the meter scale and the background piece, and unscrew one of the screws for the galvanometer and swing the galvanometer aside. Push in the rangefinder roller and pull the rangefinder assembly up and around the bits of the shutter that are over the RF mirror.
Figure 2: RF assembly removed, light meter galvanometer moved aside
I have no idea how the prisms are held in place. Glue? Glass magnets? Centrifugal force? Whatever. I used the trivial approach and left all of the major optical components in place, with the exception of the frame lines mask. It comes off with two screws at the base of the mask assembly. Mine had washers underneath, one under each screw (presumably important). The lens nearest to the eyepiece also comes off easily, with one screw.
3. Cleaning
So this finder had lots of fungus and a bit of haze. To remove the fungus, I use my usual secret weapon: a bit of moisture and foul stench from my breath, and a cotton swab or piece of toilet paper wrapped around a screwdriver or whatever. With luck, the fungus hasn't etched the glass and will come off easily. This time we were lucky.
Figure 3: Fungus on framelines prism
Figure 4: Fungus removed!
The space between the beamsplitters can be accessed with a small cotton swab thing, or something like that. You'll have to remove a light shield and remember to glue it back later.
Figure 5: Cleaning between the beamsplitters
4. Reassembly
The only hangup I had was in getting the framelines moving. There's what looks like a screw on the lever C9312, but it's riveted in the back. I thought it was an eccentric to adjust the framelines but it was hard to turn. And then the framelines would stick when the rangefinder cam was pressed. That screw thing is actually just a slotted cylinder, the slot being there to adjust the diameter of the cylinder such that there is no slop as the framelines mask translates for parallax correction - if slop is there, then the frame lines will change as the mask moves. So yeah, it looks like a screw but don't turn it.
Actually I got hung up on a couple of things.
The shutter button is not symmetric - one of the slots is deeper than the other. The deeper slot goes where the rectangle thing is on the piece underneath, otherwise the A-R ring will jam.
And then when I was doing the final checks after assembling the camera, I noticed the vertical alignment was off. So I tried to fix it through the access hole since the top cover was on. If the shutter is set to 15 or 30, the vertical alignment eccentric is blocked by a lever. And even with that out of the way I found it difficult to find the eccentric - and eventually I got the screwdriver between the eccentric and the RF mirror, and broke the mirror free from the metal. A classic move - break the camera during the final checks.
5. Rangefinder and frame lines alignment
Once I had stopped swearing and glued the mirror back on, the horizontal alignment was way off. Underneath some anti-reflective material near the mirror are two screws, labeled S 1528 in the manual. One of them wouldn't come loose, but the other did (the RF was in place at this point, and I was trying to use the screwdriver around stuff) and with the one closer to the eyepiece loose you can pivot the bracket that holds the mirror around a bit. Use this to get your horizontal alignment within the correct range.
Screw C 2419 is the fine adjustment of the horizontal alignment. For gain adjustment (if infinity is good but 1m isn't), you'll need to make a tool to rotate a cam underneath the RF roller - a 6mm spanner that's 0.030" or something thick, really thin. I never bothered adjusting this. Tightening the screw on the RF roller didn't seem to be good enough to turn the cam.
All of the rangefinder adjustment points are accessible without removing the top cover; the vertical adjustment and fine horizontal adjustment are under screws.
6. Optical diagram
There doesn't seem to be the optical diagram for the Canon 7 viewfinder on the internet, so here is my take on it; from the repair manual drawings and what I can see with my finder partially disassembled. So you're warned, it's correct as far as I can tell, but I could be wrong.
Figure 6: Canon 7RF/VF optical diagram
Figure 7: Front and bottom views
Figure 8: Front and back views
Figure 9: RF and framelines beamsplitters
Figure 10: Framelines assembly components.
Figure 11: Framelines mask
Figure 12: Framelines mask, reverse (side facing aft)
Figure 13: Exploded diagram of RF/VF from repair manual
The interesting thing about the Canon 7 viewfinder is that there are two beamsplitters. One for the rangefinder, with just the centre area semi-silvered; and one larger beamsplitter for the frame lines. This explains why the rangefinder spot does not move with the frame lines as in a Leica; the rangefinder image does not pass through the framelines mask. The frame lines assembly is quite complicated since it has four settings (35/50/85+100/135), and changes frames by having a mask translate horizontally. The rangefinder on the other hand is as simple as it can be, with only a moving mirror. An interesting approach to making a simple, but quite good, rangefinder (I wonder if it's any cheaper than a Leica-style finder though).
7. References
Canon 7 repair manual
Hans Kerensky's Canon 7 notes
MaxElmar
Well-known
Thanks!
Thanks!
Hey Mooge -
Well done, man. Very helpful.
Thank you!
Thanks!
Hey Mooge -
Well done, man. Very helpful.
Thank you!
