Calibrating focus on MF Folder

[Chadinko]

Forgive me if I sound like a total noob because I am a complete noob at this stuff. I feel like I'm asking all these questions and not offering any help to anyone. Maybe someday I'll know enough to do that.

I have a beautiful Voigtlander Bessa Braunschweig that, oddly, I got at Goodwill... it looks to be all original and it's in lovely shape. When I got it, there are no light leaks but the shutter was sluggish so I did some housekeeping on the shutter to free it up. Took the camera out yesterday and every single image beautifully exposed, well-composed (the Brilliant finder is nice), and blurry. I've been reading about calibrating infinity focus on front-cell focusing lenses (there was a url link here which no longer exists) but I'm still fuzzy on what's wrong with this one.

I grabbed a ground glass from an old springback Speed Graphic and taped it, ground side towards the lens, to the film guide rails in the back of the camera to simulate the film with the backing plate pressed against it, and I cannot get a focus at all on the glass no matter whether the lens is screwed all the way in to the shutter or all the way out to the end of the threads. The outer cover with the infinity stop is currently off the lens as I am trying to find infinity so I can reinstall it and use the camera.

The ground glass is, as far as I can tell, in the same position that the emulsion would be if it were film, so I'm really puzzled as to why I cant find a focus at all on it.

The lens has no helical except the threads, and threading it back and forth doesn't seem to affect the focus that much. When I removed the shutter, there were no spacers or anything between the front standard and the shutter, so when I reassembled it I just reassembled it exactly as it was when I took it apart. I did not disassemble the lens elements, as they are beautifully clean and clear and barely needed cleaning.

Any ideas as to where I might start?

 

[Nick Merritt]

Sounds like you've done everything right -- can you tell if there's a point that's in better focus than anywhere else? I'm wondering about a couple of things: 1) whether the front element is on the "wrong" helical -- often there's more than one thread starting point (this is mentioned in that other discussion you linked to) or 2) the second element was (re)installed backwards, though I think with this second alternative, you'd have better results than you're getting.

 

[Alan9940]

Don't know if this will help, but I had a somewhat similar situation with my Zeiss Super Ikonta III, except that it refused to focus where I set it via the rangefinder. I, too, put a small length of groundglass against the film guide rails and attempted to adjust the rangefinder at both infinity and its closet focus position. After several attempts to resolve the issue on my own, I sent it off to Ken Ruth at Photography on Blad Mountain (before he retired...thankfully) and it turned out that the front "standard" was not aligned correctly with the film plane, and there were a few shims missing from inside the shutter/cell assembly. All fixed now, but those issues are not anything I could have figured out on my own.

Good luck!

 

[shutterfinger]

What lens is in the Bessa?
Can any degree of sharp focus be obtained by moving either the ground glass further back from the rails or the front standard closer to the camera body with the gg against the rails?

 

[Chadinko]

Sounds like you've done everything right -- can you tell if there's a point that's in better focus than anywhere else? I'm wondering about a couple of things: 1) whether the front element is on the "wrong" helical -- often there's more than one thread starting point (this is mentioned in that other discussion you linked to) or 2) the second element was (re)installed backwards, though I think with this second alternative, you'd have better results than you're getting.

I read about the "wrong helical" thing in the other thread, but I don't think so. When I read that, I unscrewed front element and rolled it around and tried it on a number of different starting threads and I got exactly the same result. I can't see that which helical the element is started on makes a difference, since unlike some of my MF SLR lenses, it's not really a helical so much as a thread pitch, and being uniform it should thread in and out at the same rate regardless of where it starts.

I think that the second element only goes in one way? I'll check the element but I'm pretty sure it's installed in the correct orientation. I can take it out and look but I don't think it's in backwards.

What lens is in the Bessa?
Can any degree of sharp focus be obtained by moving either the ground glass further back from the rails or the front standard closer to the camera body with the gg against the rails?

It's a Compur Rapid shutter and a 105mm f/4.5 Skopar. I haven't tried moving the glass... never thought of that. I'll give it a try in a few minutes and see.

Edited to add: I'm not sure I can move the standard closer to the body -- it's a Bessa (my other Voigtlander folder is an Avus) so it's self-erecting. Is there a way to adjust the position of the standard?

 

[shutterfinger]

I was thinking in terms of a standard that pulls out from the body, some brands do.
This is the lens diagram for your lens. Light travels the direction of the arrow.

You will have to disassemble the cells to verify the correct orientation. I suspect someone took it apart and cleaned it then assembled it with the elements in the wrong direction.
You can also unscrew the rear cell in 1/4 turn increments and see if it improves the focus then shim as needed.

 

[Luckless]

Can you completely remove the lens from the camera reasonably safely and have it in a functioning form apart from the rest of the body? If so then building a test rig out of a shoebox or something to confirm that the lens assembly can achieve a reasonably sharp focus (a camera obscura kind of rig is easy enough to build with some basic tools) has always seemed like a good starting point when dealing with unexpected results out of a lens in my mind.

There seems to be little point in fiddling with an entire camera body when trouble shooting focus till you have a lens you know focuses reliably.

As someone who has done weird tinkering with optics, I tend to assume that it isn't impossible that someone else has done weird and random tinkering with old optics before they got to me. You could have someone's failed attempt at some weird experiment after all. That's part of the fun of picking up really old camera gear from odd sources after all.

 

[tedr1]

Yes I think you are right, the orientation of the multi-start helix doesn't matter, until the engraved focus distance ring is attached, then it matters.

 

[Chadinko]

I was thinking in terms of a standard that pulls out from the body, some brands do.
This is the lens diagram for your lens. Light travels the direction of the arrow.

You will have to disassemble the cells to verify the correct orientation. I suspect someone took it apart and cleaned it then assembled it with the elements in the wrong direction.
You can also unscrew the rear cell in 1/4 turn increments and see if it improves the focus then shim as needed.

I'll check. I don't really want to disassemble it unless it's the last thing I try. The Avus I have has a standard that pulls from the body, but the Bessa is self-erecting. Otherwise they seem to be about the same body.

Can you completely remove the lens from the camera reasonably safely and have it in a functioning form apart from the rest of the body? If so then building a test rig out of a shoebox or something to confirm that the lens assembly can achieve a reasonably sharp focus (a camera obscura kind of rig is easy enough to build with some basic tools) has always seemed like a good starting point when dealing with unexpected results out of a lens in my mind.

There seems to be little point in fiddling with an entire camera body when trouble shooting focus till you have a lens you know focuses reliably.

As someone who has done weird tinkering with optics, I tend to assume that it isn't impossible that someone else has done weird and random tinkering with old optics before they got to me. You could have someone's failed attempt at some weird experiment after all. That's part of the fun of picking up really old camera gear from odd sources after all.

I can pull the lens and shutter from the camera; it's fairly easy. The challenging bit is getting the thing back together, since the bellows are in really good condition and fairly stiff and I'm not an octopus. I can throw it on the Avus and move the standard in and out, or if all else fails stick it on one of my baby Graphics and see if I can get a good focus with it that way.

 

[Leigh B]

I read about the "wrong helical" thing in the other thread, but I don't think so. When I read that, I unscrewed front element and rolled it around and tried it on a number of different starting threads and I got exactly the same result. I can't see that which helical the element is started on makes a difference, since unlike some of my MF SLR lenses, it's not really a helical so much as a thread pitch, and being uniform it should thread in and out at the same rate regardless of where it starts.

You're correct The choice of starting position will not change the characterisics of the lens in any way.

- Leigh

 

[shutterfinger]

since the bellows are in really good condition

Go to your local leather store and get some pure Neatsfoot Oil. Clean the bellows and body leather with 90% Isopropyl Alcohol and a clean towel then apply two or 3 light coats of the Neatsfoot Oil with a cotton ball and allow to dry between coats. Support the bellows from the inside while cleaning/treating.

 

[Saganich]

Either the front assembly is not parallel with film plane or one of the elements is backward or not aligned. Ground glass can help figure which problem.

 

[Chadinko]

Go to your local leather store and get some pure Neatsfoot Oil. Clean the bellows and body leather with 90% Isopropyl Alcohol and a clean towel then apply two or 3 light coats of the Neatsfoot Oil with a cotton ball and allow to dry between coats. Support the bellows from the inside while cleaning/treating.

Thank you. I will do that. I have some Neatsfoot oil already, hadn't thought of doing that.

Either the front assembly is not parallel with film plane or one of the elements is backward or not aligned. Ground glass can help figure which problem.

Yeah when I get a chance, probably this evening, I'll check it further and try to sort it out.

 

[Chadinko]

I figured out what the focus problem was on this camera. The front element is in two parts -- the lens part and a barrel that screws into the shutter. I didn't remember from when I disassembled the thing that the barrel remains stationary and the lens part is the one that rotates. I still need to fine-tune the infinity focus a little but I made some progress last weekend.

 

[pentaxpete]

I found about that lens being kin 'two parts' when I took out the lens from my 1956 Agfa Isolette III with Solinar lens and Compur-Rapid shutter. I was looking and saw a 'join' so I picked up a very small drop of WD40 onto a pin and put it in the join and twisted and LO !! and BEHOLD ! -- the two parts separated and I could set the focus again and it has been OK ever since !

 

[Chadinko]

I found about that lens being kin 'two parts' when I took out the lens from my 1956 Agfa Isolette III with Solinar lens and Compur-Rapid shutter. I was looking and saw a 'join' so I picked up a very small drop of WD40 onto a pin and put it in the join and twisted and LO !! and BEHOLD ! -- the two parts separated and I could set the focus again and it has been OK ever since !

My Isolette (I think it's a I) is the first camera I attempted a shutter rehabilitation on. I had bought it from Goodwill for stupid cheap and it's in cosmetically quite good shape, but the shutter was gluey as is fairly normal.

I took the top off the shutter and then did something else and all the shutter blades went PING and fell out all over the table. Scared the poodiddles out of me and I bagged up the whole thing and placed it in a drawer which has since become the Island of Lost Camera Parts. After rebuilding a number of Compurs on assorted Voigtlanders, I ran across this shutter the other day and thought it'd be fun to try to reassemble it. It went right back together, no lost parts, works well enough as far as I can tell, and THEN I discovered that the lens is hazy and has some fungus that I can't get rid of. Damn. If I can find an Isolette that's trashed but has good glass I'll probably make the exchange because it's such a pretty thing I want to use it.

Now onto the Seikoshas...