Voigtlander Perkeo II focus calibration

[David A. Goldfarb]

Does anyone here know how to adjust the focus calibration on the Voigtlander Perkeo II? I'm guessing there's some sort of set screw for setting the infinity stop and the distance scale relative to the position of the lens in the helical. The lens is the front-cell focusing 80/3.5 Color-Skopar. I always make sure the front standard is locked into place when I open the camera.

I noticed a whole roll was out of focus a few months ago, including some shots where the lens would have been set at infinity in daylight, so probably stopped down to at least f:11, and they were made on different days, so I can't have forgotten to focus all those shots. I set the camera aside thinking it was just the uncoupled rangefinder calibration, but tested today, and the rangefinder is working perfectly. I put some wax paper across the film gate, and it's clear that the focus has shifted.

Anyone who has worked on this?

 

[DWThomas]

My guess would be it's the three tiny setscrews in the ribbed section around the lens just forward of the focus scale. That's where I would start, but I'm pleased to report I've not yet had reason to try it.

 

[David A. Goldfarb]

That's what I'm looking at, but if someone's done it, it would be good to know. Whenever I take apart something with a helical, there's always that uncertainty about putting it back the way it came apart.

 

[02Pilot]

Yes, as mentioned, the three set screws come out to release the ring that holds the front cell and contains the infinity stop. Been a while since I had mine apart, but that much I remember. The only other thing I can think of that would cause uniformly out-of-focus images would be if the retaining ring for the shutter/lens assembly somehow loosened up.

 

[alienmeatsack]

On all of the folders I have the above mentioned focus ring and it's 2-4 grub screws (depending on make/model) are usually the culprit. That focus ring can move or get loose if the grub screws aren't in place right. Or if the lens assembly has gotten stiff and when turning the focus ring it slides instead of moving the lens. The AGFA I purchased recently was like that. The focus assembly had frozen and the previous owner had tried to move it and caused the grub screws to dig a trench into the outside of the lens metal itself.

To set focus, I use some waxed paper or tracing paper over the back with the camera on the widest aperture. I aim it at something bright and sharp that I know is exactly 1 meter away and adjust the focus so the image on the waxed paper is in focus. I note the focus ring's position and how far off it appears to be, then loosen the grub screws, adjust, and gently tighten the grub screws, then try 3 meters and then infinity, to see if I got it aligned right. If it's off, I'll loosen the grub screws, adjust the ring to compensate, re-tighten and check my close focus zones again.

Once I'm sure it's close, I'll shoot a roll on the widest aperture at each focus zone to make sure it's good. If not, I repeat the process.

There should be at least 1-2 stop posts in there that are what stops the ring itself from going past the close and far focus areas, so it can't spin too far in either direction. Adjustment is probably just a very minor movement of the ring itself to get focus.

 

[gone]

On most front cell focusing folders, there's an infinity stop on the inside of the front bezel. I have a different way of setting focus. If you have a piece of ground glass to tape over the film rails it will be a lot easier to see than paper. I use a loupe, or an SLR lens used as a loupe, to get things correct.

Loosen the 3 grub screws and take the front bezel off the lens. Looking at the back, you should see how the infinity stop works. Put the camera on a tripod, focus on something about 100' to 150' away, and turn the front element until you have sharp focus on the ground glass. Then, w/o moving the element, slip the front bezel on, turn it (again, w/o turning the element) to where the infinity stop bottoms out, and tighten down the grub screws. Double ck the ground glass image to make sure nothing accidentally changed during the tightening up of the screws.

There's really no reason to ck it at any other distances, because if you do, and readjust things, you'll throw off the infinity focus. You don't have any other adjustment on these, other than paper shims between the shutter and lens board, and if you haven't removed the shutter that shouldn't have changed. If you have sharp infinity focus, then all the other distances will be correct.

If you DO remove the shutter and possibly lose/misplace those shims, the focus setting procedure will be different, as you'll be using the shims to set the infinity, along w/ the front cell infinity stop. If you somehow unscrewed the front element off the helicoil threads w/o marking the point where it came off, you're set for some fun. There's probably a half dozen places where you can start the threads, but only will be the right place. It's usually the last place you try too.

 

[David A. Goldfarb]

Thanks for all the pointers! These are great.

Now I realize I've got to go to my storage unit and find my tiny screwdrivers, which I still haven't unpacked since the move earlier this year.

 

[David A. Goldfarb]

Momus' description is right on target.

I loosened the three grub screws without completely removing them, and the bezel slipped off.

There's a fixed stop on the lens and two fixed stops on the back of the bezel, indicated in the photos attached.

I taped some wax paper across the film gate. The best magnifier I had for this purpose was a Zacuto finder that I use for the LCD screen on my DSLR, because it's wide enough to go flush across the film rails and the rollers without deflecting the wax paper. A chimney finder from a medium format SLR or a rectangular loupe for viewing 6x7 transparencies might work as well.

I focused the finder on the surface of the wax paper and then focused the lens with the aperture wide open at an object at infinity. A groundglass would be better, but I don't have one handy.

I replaced the bezel with the infinity stop lined up with the stop on the camera, tested at 4 feet, then did it again until both distances tested right and it agreed with my uncoupled rangefinder, which seems to be properly calibrated.

Next I test with film.