Bronica SQ 50mm lens question

[JPD]

Yes that's a good question and then, what is the distance from the paper to the lens mount, compared with the distance between the lens mount on the body and the film plane ?

Yes! Or hold it side by side with another Bronica lens that is known to work. Ideally they should both project the infinity image at the same distance from the paper even if they have different focal lengths.

I have a white fridge opposite the kitchen window that I use for simple experiments like checking the focal length of single lens elements or the front and back components of convertible lenses.

 

[Horatio]

Yes! Or hold it side by side with another Bronica lens that is known to work. Ideally they should both project the infinity image at the same distance from the paper even if they have different focal lengths.

I have a white fridge opposite the kitchen window that I use for simple experiments like checking the focal length of single lens elements or the front and back components of convertible lenses.

I’ll check tonight. Rubber flange thingies on the way, thanks to Amazon.

 

[choiliefan]

Some lenses use a bit of thread-locking "glue" which may have to be softened with a thinner before disassembly.

 

[Horatio]

With the focus on infinity, the 50mm lens produces a focused image at a distance of about 60mm from the breech lock. The 80mm lens produces a focused image at distance of about 90mm. The 80mm image seems larger. So, the lens CAN produce a focused image, just not at the film plane. I did locate a schematic for the 50. It has 11 elements in eight groups (see below). It seems possible to reverse one of the central elements, so that's what I'll look for as soon as I can get into it. IF, I can get into it. lol I think I found the spot of locktite as well.

 

[Grim Tuesday]

Very interesting result! The third element from the back looks like it could have been easily reversed, if it is loose and not part of the group. Loctite can be dissolved with nail polish remover or acetone. Put it on a Q-tip and then press against the affected area, making sure it wicks into the threads. But also don't pour it on. Keep us posted, I am very interested to see what you find out!

 

[polka]

The difference of focusing distance that you measured seems so large that I think could not be explained by simple element reversed.
As the lens is a typical retrofocus, my guess : one of the two divergent lenses in the front (the 2nd or the 3rd) is missing. (or both ? or maybe the cylindric element in the middle ?)
POLKa

 

[RalphLambrecht]

It does not focus on anything. The groundglass remains OOF. The split microprism does not change. Where would one find this "expansion ring"? It's appearance is similar to my other lenses.



I'll post a better photo tonight.

there doesn't seem to be an extension ring on it!

 

[Horatio]

So far I’ve only succeeded in removing the nameplate and the retaining ring for the outermost element, which I put back. Hmmm. I’ll have to give this some more thought over the weekend.

 

[Horatio]

Still working on getting the front elements out. Does anyone know they come out as a group, or one at a time? I got the rear elements out easily, and confirmed the fourth element from the rear is properly oriented.

 

[Grim Tuesday]

Still working on getting the front elements out. Does anyone know they come out as a group, or one at a time? I got the rear elements out easily, and confirmed the fourth element from the rear is properly oriented.

What is holding them in? Spanner nut or have you already removed it?

By the way, to see if an element is missing you can count reflections (one bright reflection per air-glass interface, one very dim almost imperceptible reflection per glass/glass interface). It will be easier with the rear elements removed.

 

[Horatio]

Got it apart, and (miraculously!) back together. I reversed the center elements (one piece assembly) but it made no difference. It’s like it’s in macro focus. My fingers are in focus when I hold them directly in front of the lens.

I'll take it apart again this weekend.

 

[moto-uno]

Well if nothing else , Good for you on getting it apart . Careful though , you might find this fun . Peter

 

[Grim Tuesday]

It's so very strange that your lens is like this. I wish there was more advice I could provide, but if you counted all the elements, and they are all there, and in the right direction, and in the right place, then they can't be the problem. I would suggest that maybe the helix has been disassembled and re-assembled wrong, but I think that would cause focusing problems at infinity, not the extreme focusing problems at all distances you are experiencing. The only other thing I can think of is a complete seperation of an element, and that element being removed. But complete separation is a massively major rarity, I don't think I've ever seen it, it would almost be so rare as to be something that can only happen at the Zenzanon factory. This lens might be a lost cause.

Like @moto-uno said, be careful of finding this fun! After I figured out how easy it was to take apart lenses, I took most of mine apart and cleaned out what I had previously thought to be minor haze and image sharpness and resolution was massively improved. This is on Pentax 6x7 lenses, almost all of which have haze at the elements near the aperture from whatever lubricant Pentax used on the helix. And, this is a topic for discussion, but after reading repair manuals from Hasselblad and Zeiss, I have come around to the opinion that when disassembling and re-assembling lenses, the tilt and rotation of the elements doesn't matter in the case of these lenses (in modern zooms, it would) so I do not find that to be a major deterrent.

 

[Horatio]

It's so very strange that your lens is like this. I wish there was more advice I could provide, but if you counted all the elements, and they are all there, and in the right direction, and in the right place, then they can't be the problem. I would suggest that maybe the helix has been disassembled and re-assembled wrong, but I think that would cause focusing problems at infinity, not the extreme focusing problems at all distances you are experiencing. The only other thing I can think of is a complete seperation of an element, and that element being removed. But complete separation is a massively major rarity, I don't think I've ever seen it, it would almost be so rare as to be something that can only happen at the Zenzanon factory. This lens might be a lost cause.

I want to count the elements again this weekend, when I'm fresh. I got interrupted tonight. I suspect a central element is missing.

Like @moto-uno said, be careful of finding this fun! After I figured out how easy it was to take apart lenses, I took most of mine apart and cleaned out what I had previously thought to be minor haze and image sharpness and resolution was massively improved. This is on Pentax 6x7 lenses, almost all of which have haze at the elements near the aperture from whatever lubricant Pentax used on the helix. And, this is a topic for discussion, but after reading repair manuals from Hasselblad and Zeiss, I have come around to the opinion that when disassembling and re-assembling lenses, the tilt and rotation of the elements doesn't matter in the case of these lenses (in modern zooms, it would) so I do not find that to be a major deterrent.

Yes. This could become habit forming! There's some fungus on my 90mm Elmar I want to clean. Now I'm emboldened to try.

 

[choiliefan]

Sounds to me that the focusing helical isn't set properly to its stops.
If you could compare yours to an identical lens, set both at infinity and measure the distance from the rearmost lens surface to the mount, you would know, no?

 

[Grim Tuesday]

Sounds to me that the focusing helical isn't set properly to its stops.
If you could compare yours to an identical lens, set both at infinity and measure the distance from the rearmost lens surface to the mount, you would know, no?

I thought that too, but it would have to be REALLY messed up for what OP is reporting. But now that OP has ruled out the more likely things, maybe this is it.

 

[Horatio]

Sounds to me that the focusing helical isn't set properly to its stops.
If you could compare yours to an identical lens, set both at infinity and measure the distance from the rearmost lens surface to the mount, you would know, no?

Maybe, but I’d have to buy an identical lens to do that!

How does one adjust the helical?

 

[choiliefan]

Perhaps someone reading this will measure their lens and reply?

 

[moto-uno]

^^ Be very careful when playing with helicals , it can become a nightmare of endless re & re 's . When I sense I may be getting close to when
it suddenly falls into your hand , I have a felt marker handy and the moment it releases I put a mark on the 2 matching surfaces . But I'm not
overly convinced this may be it . My experiences ( not many ) have still allowed the lens to focus through much of it's travel , just not at the extremes.
And also the lens distance marks are usually noticeably off . Peter

 

[Veselin Mihaylov]

Maybe, but I’d have to buy an identical lens to do that!

How does one adjust the helical?

At infinity the rear element protrudes from the mount about 4mm.
Unfortunately at the moment i don't have a caliper to measure it correctly.

 

[Horatio]

At infinity the rear element protrudes from the mount about 4mm.
Unfortunately at the moment i don't have a caliper to measure it correctly.

It's measuring 4mm exactly at infinity.

 

[Horatio]

Took everything apart yesterday and tried reversing the end element of the large assembly. No change.

 

[choiliefan]

Did you have to unscrew the helical to do this?

 

[Horatio]

Did you have to unscrew the helical to do this?

If by helical you mean the mechanism in the lens barrel itself, apart from the elements housing, no. The helical moves to and fro just like my other lenses.