Zeiss Ikoflex Viewing Lens Reassembly?

[BHuij]

Several years ago, I inherited a nice Zeiss Ikoflex Ia with an excellent Tessar 75mm f/3.5 taking lens. I put several rolls through it and they came out great. Everything was in working order, but also very stiff and kinda grimy. This was in 2016 or so.

In my infinite wisdom, I decided to do a bit of disassembly and try to clean some lens elements and whatnot. Nothing too serious, and I did get everything clean on the viewing lens (a Teronar-Anastigmat f/3.5). Unfortunately I didn't pay close enough attention to how it all came apart, and managed to get it back in wrong. From that point forward I couldn't get good focus with it. Seemed odd and not quite... flat? Like the center could be in focus, but the edges would be way out of focus and smeary-looking. Wasn't like that before I disassembled and reassembled it.

Luckily I had the common sense not to touch the taking lens. I quietly put this camera back on the shelf and went back to shooting my Yashica Mat 124 when I was feeling in a 6x6 mood.

Now here we are 8 years later, and I want to get it back up and running. I have disassembled the viewing lens completely. Below is a photo and description of what I *think* each piece is. Looking at diagrams online, this lens appears to be a cooke triplet design. Front and rear elements that are both convex on one side and flat on the other. A middle element that is concave on both surfaces.

Anyone think they could help me get things back in place properly? It looks like once it's back together into the housing, it's a fairly simple matter of screwing it back into the camera body right up until it matches infinity focus with the scale, and then locking in place with the retaining ring.

A: Front element (convex and flat sides)
B: Middle element inside a housing ring (two concave sides, one slightly more so than the other)
C: Rear element (convex and flat sides, just slightly smaller in both diameter and concavity than front element)
D: Lens barrel
E: Trim ring or possibly retaining ring to help keep distances correct as lens assembly screws into camera body
F: Spacer; definitely fits just right on one side of the middle element housing B
G: Appears to be a ring to hold the rear element C and make up the diameter difference to keep it centered in the housing; that element fits perfectly in a small shelf here. No threads on it.
H: Rear retaining ring that keeps the entire assembly in place inside the barrel. The outer threads fit the inside of the lens barrel. There are notches cut for a spanner. Oddly it has inner threads too; not sure what those would be for.
I: Screws over the lens barrel D and interfaces with E; can be locked to the barrel with a set screw at any point. I think E and I work together to help lock the lens assembly at the correct distance from the body when installed.

Very open to suggestions on how to get this put back together.

Update after an evening of listening to my college football team lose and messing with various configurations. Feel free to ignore if you already know the right answer. So far I've tried:

1. Not messing with E or I yet as they don't seem to control lens distance from reflex mirror in the camera body; I'm guessing they just lock it down when the correct distance is obtained by screwing D into the camera body. Inside the lens barrel D, from front to back (everything inserted from rear): Front element A, convex side facing forward. Then spacer F. Then middle element B, with slightly less concave of the two sides facing forward. Then rear element C inside ring G, with convex side of C facing rearward. Finally H to lock everything in place. Result: Can't get anywhere near infinity focus even screwed all the way in - but I definitely have extremely close focus (closer than should be possible with this camera). This suggests to me that the front cell is too far forward.

2. All orientations the same as attempt #1, but spacer F is moved to sit between the middle and rear elements instead of the front and middle. Now the front and middle elements are touching. Result: Much closer to correct, it seems. Can't quite get infinity, but error goes the opposite direction now. I have no close focus, and I reach infinity when the assembly is held about 2mm forward from where it can touch the threads of the camera body.

3. Everything the same as #2, except I flipped middle element B around, so the more concave of the two surfaces faces forward now. Result: I can now reach infinity focus while the lens is screwed into the camera body, but I have a very strong blooming/haze effect and nothing is particularly sharp even when in focus. I confirmed this isn't due to smudges on the glass anywhere, it's all clean.

I'm calling it for the night. Still open to suggestions for what to try!

 

[ic-racer]

 

[ic-racer]

Is your lens "C" biconcave? If so, orient it so the sharper curve is toward the film. Then fiddle with the spacing.

 

[BHuij]

I don't believe it is, appears to be flat on one side and convex on the other. But it's possible it's slightly convex on the side I'm calling "flat". In any case, worth a try!

The more I play with it, the more it seems there are certain pieces that really only belong together in one way. The rear element, I suspect, is where my issue is.

 

[BHuij]

Just to clarify, I had front element A facing with curved side away from the film. Then B, which is biconcave, with the more curved surface towards the film. Then a spacer, and then rear element C, which I think is just convex on one side and flat on the other, but may be biconvex, with the obviously curved side towards the film.

Without realizing that you may have mixed up something in your comment, I just flipped the rear element so the curved side (or possibly just the "more curved" side) was facing away from the film instead of towards it. It... might have helped. I might be able to just barely get infinity focus at the very edge of how far out I can have the assembly without it running out of threads and coming disconnected from the camera body.

Can't help but think when it was first given to me and I had not yet disassembled it, that the lens assembly was screwed several mm further into the camera body and was of course still giving perfectly good infinity focus.

I'm running out of ideas here. Can't imagine the front element needs to be curved towards the film instead of away from it. The spacer/housing rings for the middle element seem to really have only a single way that makes sense for them to fit together, though I've tried taking some liberties anyway.

I'll keep researching and tinkering, and am still very open to suggestions

 

[ic-racer]

Maybe I mistook the picture. Is "A" the front and "B" the rear doublet? With "C" the middle biconcave lens?

 

[Dan Daniel]

In typical Zeiss fashion, they appear to have chosen a complex way to handle a simple problem, focus of the viewing lens. Looking at two different Teronars, each is a simple silver tube holding the lens elements. I'll let you figure this out. Below is a Rollei diagram of their viewing lens and I bet Zeiss used something similar- basic triplpet, larger curves facing front and back. Middle element, I forget- you can feel the difference in the curve with your finger tip. Assemble one way and if it gives a milk bottle effect, reverse it.

I have one lens with a simple 'lock ring' on the silver tube's threads- maybe your E? And one with a piece more like I. Two separate peices, not meant to work together? Seems as if each would serve a a lockring after screwing silver tube into lens board threading and getting focus there.

Maybe yours has no threads on lens board and E is a rear lockring, backside of lens board?

Does your lens board have threads?

 

[BHuij]

Maybe I mistook the picture. Is "A" the front and "B" the rear doublet? With "C" the middle biconcave lens?

A is the front element (flat on one side and convex on the other). B is the middle element (biconcave with one side noticeably more curved than the other). C is the rear element (I believe flat and convex). Each element is a single piece of glass, I have no doublets here like I assume are in the taking lens (which is definitely a Tessar).

I've drawn up some diagrams of assemblies I've tried; I'll post them when I get a minute so it's easier to visualize what's going on.

From what I can tell, it should be a fairly simple matter of getting the orientation and spacing of each of the 3 glass elements correct inside the silver tube. It appears to be set up such that the elements and spacers all just butt up against each other to hold rigid and correct spacing and alignment along the tube axis, and then everything gets locked in with the rear retaining ring that goes into the barrel from the back at the very end. Once the optical assembly is put together in the tube, the tube itself screws directly into the lens board on the camera body. It's a pretty long thread, seems designed to allow the entire viewing lens assembly to thread way in until infinity focus is reached properly. Pieces E and I seem to just be there to allow for a nice trim ring and a finished-looking front when everything is said and done. The camera would function just fine without them, from what I can tell.

The common thread with everything I've tried is that when I go to screw the finished assembly back into the lens board (which is set at infinity focus), I get objects at infinity in focus on the focusing screen when the lens threads haven't yet engaged. Sometimes it's close, but even the times I feel like I've managed to get proper infinity focus while the unit is screwed into the board, it's very nearly at the end of the threads and protruding quite a bit. When I first disassembled this lens, it was definitely screwed in far further back towards the film plane (something like ~1cm or even more).

Finally... just to throw one more stupid variable into the mix, I pulled the focusing screen and fresnel lens out of the hood because they were in desperate need of cleaning. After thoroughly dusting both, I'm now no longer confident that I got them back in in the right order. Apparently I haven't learned my lesson on this particular camera vis a vis paying attention while I disassemble.

I believe the fresnel glass is orientation-agnostic, it doesn't seem to behave differently no matter which side I look through. So flipping it over shouldn't have any effect. But now I need to figure out if it goes above or below the frosted glass proper. If it's like any other ground glass I've used, the frosted surface of the glass should be down towards the mirror and the smooth surface up towards the viewer, but I don't know if the fresnel is designed to sit above that or below it. That would definitely affect focus, as the fresnel is easily a couple of mm thick. Though if my understanding is correct, it would only account for about the thickness of the fresnel in one direction or another in terms of how much more/less threading in I should have to do with the Teronar lens assembly.

Drawings to come

 

[BHuij]

Here are the 4 orientations that have been the least disastrously wrong

Left side is the front element facing towards the scene, right side is the rear of the assembly facing toward the film plane. Hopefully this clarifies.

 

[ic-racer]

Ok, I see now.

This might require someone with the same camera to chime in.

 

[Dan Daniel]

Focus- glass to top (closest to your face when focusing), smooth to top (facing face). Best to put the fresnel with grooves against the ground glass.

On center lens element, the deeper curve faces back.

I didn't notice on first shot that there is a thin black ring around the rear lens element. The lens sits in this with glass to front, lip on ring to back. Then overall lock ring/retaining ring sits on it. The curve faces out on both front and rear elements

 

[Patrick Robert James]

I have an Ikoflex but messing with the lens would require it to be reset, so….

The Teronar is just a triplet, so here is a diagram of a Triotar. Should be the same-ish.

Usually you can tell where an element “seats”. Are A and C the same diameter? Maybe you have them flipped.

 

[Patrick Robert James]

I didn’t see Dan’s post. Excellent!

 

[BHuij]

Thanks for the very good pictures. I think what you’re saying is correct matches my “attempt #3.” Any guesses why it might want to be so far away from the film plane in order to reach infinity focus?

 

[Dan Daniel]

No spacer between A and B?

 

[BHuij]

No spacer between A and B?

Nope. When I tried with a spacer between the two it made a macro lens that focused about 3 inches in front of the front element and no further.

 

[BHuij]

Okay I got it! Thank you so much for disassembling yours to show me. I had the very first spacer ring behind the front element flipped the wrong way, so the biconcave middle element was too close to the front. As soon as I got it set up as you showed in your photo, and got my fresnel/ground glass situation rectified, it screwed right in and was easy to find infinity focus, right where I expected it to be. Everything is locked in now and should be dead-on. I'll put test roll through it to make sure I'm not seeing de-synchronization between the viewing and taking lenses.

 

[BHuij]

I'm putting a roll of film through this camera right now to confirm whether I properly collimated my viewing lens. After exercising the shutter for a while, I got to the point where it would fire reliably at every speed. I haven't done any real measurements yet, but it's clear that the speeds between 1 second and 1/10th or so are significantly slower than nominal. Furthermore, the shutter release button needs to be pressed very firmly to trip the shutter, and using a cable release doesn't work at all. And when I cock the shutter, sometimes one of the leaves moves enough to let a bit of light through to the film plane. Finally, the focus knob is working but stiff, which seems to be a common problem.

I'm well out of my depth trying to repair a Prontor S or SV shutter (I've seen the Ia listed as having both, so I'm not sure which type is on mine). Let alone tune speeds on it.

Some googling tells me that Mark Hansen was at least at some point the go-to guy for fixing Ikoflex TLRs. I read everything on his website about the camera and he definitely seems to know his stuff. I sent him an email a few days ago but haven't heard back. I know "a few days" isn't that long to wait. Anyone know if he's still in the game?

 

[blee1996]

You just need to ask our @Dan Daniel , he might be able to service your Ikoflex if he is not too backlogged.

 

[BHuij]

I reached out to him as well, thanks!

 

[Alex Varas]

I have an Ikoflex but messing with the lens would require it to be reset, so….

The Teronar is just a triplet, so here is a diagram of a Triotar. Should be the same-ish.

Usually you can tell where an element “seats”. Are A and C the same diameter? Maybe you have them flipped.

View attachment 383709

I always have this picture when I clean the viewing lens, you can feel the most concave part with the fingers when cleaning it. The position of spacers is essential as well.

 

[BHuij]

I ran a roll through it to see if my taking lens and viewing lens focus were matching, and it came back looking great.

Shutter speeds are a bit off, but they're consistent. I found myself needing to press really hard on the shutter release button to get it to fire, and a cable release simply wouldn't trip the shutter at all. Finally, when I cock the shutter, sometimes the shutter blades (one in particular) would scoot outwards a bit and even leave a tiny hole through which light might go.

Luckily, I saw no evidence of light leaks through the front or otherwise. After examining the mechanisms pretty closely, I saw that pressing the shutter release button simply moved a little arm near the bottom of the shutter which pushed against the shutter release lever proper on the bottom of the outside radius of the shutter itself. The shutter/lens assembly was seated in a slightly rotated position in relation to the camera body, so loosening the retaining ring in the back, spinning the whole thing back towards the arm, and re-tightening has completely solved the problem.

Now I just need to do a few recordings of the shutter speeds to figure out exactly what actual speeds I'm getting, and I should be ready to shoot this camera for reals!

 

[BHuij]

Shutter speeds are consistent and usable across the board. Almost every speed is either 1/3 or 2/3 of a stop slower than nominal, so I think I'll just dial in an extra 1/3 stop of ISO on my meter when shooting this one and use the speeds as marked. Gotta remember not to do that when I'm shooting bulb, I guess