Iskra Focusing Problems

[graywolf]

OK, this starts in my other thread http://www.rangefinderforum.com/forums/showthread.php?t=101493

The camera works well except for that stiff, rough, focus.

There are several threads referred to in that thread that deal with some makeshift solutions that may or may not work. I intend to use this thread to cover some of the other causes I have found so far.

The first thing I have tried is putting some high pressure grease in the helicols. To to do that properly I would need to remove the lens/shutter/focusing unit from the camera, but as I am only in the troubleshooting mode, I just racked out the lens and applied some great old Park Polylube 1000 bicycle grease (you Isosette owners will like it, it's green) with a toothpick. The helicol is accessable from inside the bellows, since the back is removable on the Iskra that was easy to get at; you need to open the camera and run the focus all the was to one meter to access the helicol. I then ran the focus in and out several times to spread it out. The final step was to close the camera, and wipe the excess off with a Q-tip.

The grease eased the focus effort by about 50%, but there was still a roughness in the focus at certain points. Since those points stayed the same that led me to look closely at the RF linkage. I found two points that seem to be causing a problem.

Just below the viewfinder window you can see the RF linkage, it is the brass bit, rubbing against the strut. Fine brass filings were the clue. Either the strut, the RF linkage, or both are bent a bit at that point, and they are rubbing when they should not be. As a troubleshooting test, I put a bit of grease between them. That smoothed up the focusing quite a bit.

Another point where roughness seems to be caused is at the tongue of the lower RF linkage.

You can see it sticking out there at lower hinge of the drop door. Once again I used that grease as a troubleshooting test, and a bit of it eased some more of the roughness.

Now, these are old cameras, and it is quite possible that the linkages are bent. That lower linkage (the tongue part) is soft aluminum. The upper linkage is brass. Both are easily bent if the user is not careful. And, we all know how easy it is to bend those struts.

At this point, I am sure every part of the focusing and rangefinder system has to be working perfectly for the focusing to have that buttery smoothness we expect.

I hope that folks will use this thread to report any fixes they find. I will continue, off and on, to tinker until I have my camera working as well as I can make it. I also feel I need to mention again, the things I did in this post were troubleshooting devices, they are not permanent solutions to the problem.

 

[Ernst Dinkla]

The grease eased the focus effort by about 50%, but there was still a roughness in the focus at certain points. Since those points stayed the same that led me to look closely at the RF linkage. I found two points that seem to be causing a problem.

Just below the viewfinder window you can see the RF linkage, it is the brass bit, rubbing against the strut. Fine brass filings were the clue. Either the strut, the RF linkage, or both are bent a bit at that point, and they are rubbing when they should not be. As a troubleshooting test, I put a bit of grease between them. That smoothed up the focusing quite a bit.

Another point where roughness seems to be caused is at the tongue of the lower RF linkage.

You can see it sticking out there at lower hinge of the drop door. Once again I used that grease as a troubleshooting test, and a bit of it eased some more of the roughness.

Now, these are old cameras, and it is quite possible that the linkages are bent. That lower linkage (the tongue part) is soft aluminum. The upper linkage is brass. Both are easily bent if the user is not careful. And, we all know how easy it is to bend those struts.

At this point, I am sure every part of the focusing and rangefinder system has to be working perfectly for the focusing to have that buttery smoothness we expect.

I doubt it will ever get that buttery smoothness you expect. The rangefinder linking is creating only a small fraction of the friction and in a sense only on one way as it is forced out on nearby focusing but relies on its own spring to get back to infinity. If the two movements differ a lot in your case then that is certainly needing attention as it will influence correct focusing. The total of helical, focusing ring, lens tube and anti-rotating tab creates the real friction in my experience. The screws help, good greasing helps and then it ends. The lever or what should be a lever is ergonomically not very nice to use and the force you have to put on it may actually increase the friction.

Ernst Dinkla

 

[graywolf]

Speaking from a tech's viewpoint, unless those four screws have been replaced at sometime with ones that are too long. There should be no reason for them to affect the focusing stiffness. All they do is hold the front of the bellows to the front standard.

That said, I have not yet removed the lens/shutter/focusing unit from my camera, so maybe there is something that I am not seeing going on. After greasing the helical I retightend the screws evenly however, and that did not increase the focusing effort required. The focusing bump, it can not really be called a lever, is low and has sharp serrations, so is very uncomfortable to use (I get the impression it is designed to use with heavy gloves on, not an unreasonable assumption for a camera intended to be used in Russia, I would say). There seems to be a bit of clearance when the camera is closed, so I wonder if a short lever could be added to make it easier for mere mortals to move the thing.

As some of you may have noticed, I am sort of savoring this problem. Actually, I could have torn the thing down and gone through it in a couple of hours if I wanted to. Ah, well, time to run into town...

 

[Ernst Dinkla]

Speaking from a tech's viewpoint, unless those four screws have been replaced at sometime with ones that are too long. There should be no reason for them to affect the focusing stiffness. All they do is hold the front of the bellows to the front standard.

Tightening the screws most definitely changes friction on my Iskra. The screws look like being the originals. They could be too long anyway or: With a rotating focal disc/assembly in close contact with the front of the brass standard plate, in the opening of the standard and at the inside of it, any change to the planarity of that standard plate will change friction. That close contact is a condition to keep the lens in focus, pointing to the sky or earth 🙂 Tightening screws on a sandwich of two metal plates with irregular bellow fabric thickness in between creates that condition of a slightly warped stadard plate . Just another tech's opinion. The man who gave that advice in the other thread should get a (brass) medal. The design isn't optimal but design flaws like that exist in every camera I guess.


Ernst Dinkla

 

[graywolf]

At this point, while still very stiff from my point of view, my focus ring moves very smoothly. I have not yet removed the top plate to check if there is something causing the RF to drag.

The lack of heavy grease in the helical, remember this camera had been CLA'ed by the seller, was the main problem. The uneven tightening of those 4 screws was a contributing factor, my point here is that uneven tightening seems to be the problem, they do not need to be loose. The rubbing of the RF linkage seems to have been the main source of the roughness.

OTOH, the seller did a fine job on the film counter. He either fabricated or found a like new star wheel, because it just makes the faintest pinpricks in the emulsion of the film, so it is sharp and even. The counter works very well.

The shutter seems to be good too, although I do not know if it was properly serviced or just flushed out, time will tell.

I do like the EV lock, as it simplifies life a lot. Set the EV scale to 15 with ISO 100-125 film and you have your Sunny-16 exposure set. My Studio Deluxe light meter has an EV scale on it, so more complicated lighting situations are just as easily set. But, you do not really need the EV scale, set your shutter speed, pull the f/stop ring forward and set the f/stop opposite your selected shutter speed; then any combination you can turn the locked rings to are the same exposure. I can not imaging anyone who meters the light having a problem with the EV system.

 

[t6un]

Ernst,I got my brass medal in the form of a smoothly working Iskra🙂
Graywolf, have you checked the rangefinder coupling by just moving it with your finger,leaving the lens at infinity? Or focusing the lens alone while having the rangefinder coupling pulled out all the way? When I do the first, I feel almost nothing else than spring tension to pull it back. When I uncouple the rangefinder, the focusing gets a tiny bit easier, but it's already easy enough to move it all the way, in both directions, with one finger. Just like my Kodak Retina witch has a very similar focusing mechanism.

 

[graywolf]

t6un, thanks, why didn't I think of that. And, thanks for letting me know that when things are working properly, they are working properly, and that my camera has a problem to be fixed.

The RF has some roughness and extra tension at close focus. The lens gets tight at distant focus. Inspecting it, it looks like it sucked up all the grease I put on the helical, just a light oily film showing. So, I guess it needs a bit more.

Strange... I put what I consider quite a lot in there, about a match heads worth.

 

[t6un]

BTW, I see I have disengaged the little spring that pulls the "upper rangefinder linkage" towards the big spring that tensions the folding mechanism, as it seemed just redundant. There is still enough tension in the rangefinder coupling to prevent any rattle, and rangefinder follows the lens easily.
As for the "four little screws" I agree with Ernst Dinkla that they can also protrude thru the front standard. There was a black lightsealing thread between the bellows and front standard. The compressibility of this combined with the thinness of the front standard means that there isn't just the right length for the screws but also the right tightness, before one of them starts blocking the focussing ring.
Sorry, I don't recall all the problems I had with this camera at once, it's been a year since I worked on it. (Worst problem with my camera was the loose rivets on folding mechanism. Compared to fixing them, other issues seem easy now. Never open your camera without supporting the front door!)

 

[graywolf]

Been fighting an upper respiratory bug, so have not done anything with the Iskra. But it seems to be in the process of self-repair. It has just been sitting for the past few days, but I got a series vi adapter in for it and tried fitting it. Wrong size, that what I get for believing what I read on the internet, but while doing that I noticed that he focus was moving smoothly from far to near and back and is only about half as stiff as it was.

Maybe the Brownies came in and fixed it while I was laying around feeling miserable.

 

[Ernst Dinkla]

but I got a series vi adapter in for it and tried fitting it. Wrong size, that what I get for believing what I read on the internetmiserable.

It isn't as simple as fitting a VI series adapter. I use 33E filters from B&W that fit the Iskra thread. From one I removed the glass and the ring stays on the camera permanently. With a 35,5 to VI series adapter with the clamps slightly bended inwards I get a good grip on the 33E filter ring which opens up the use of VI series filters and a hood. But I also have some extra 33E filters and a flexible hood.

There still could be a Russian 33mm filters offer on Ebay that should fit the Iskra, saw it maybe a week ago.

http://www.pigment-print.com/Fotografica/Iskra/target7.html
http://www.pigment-print.com/Fotografica/Iskra/target4.html

Ernst Dinkla

 

[P C Headland]

A series V to VI step-up ring adapter should screw in one or two threads. I think the thread pitch is not quite right, but as long as you don't force it, it screw on just far enough.

The better option is the 1 3/8" or 35mm series VI adapater ring.

 

[graywolf]

One of the problems is a plethora of conflicting information on the web. For instance I have it on good authority that a Series V retainer ring has a:32mm, b:33.5mm, c:34mm, etc threads.

A Series VI adapter will fit the Iskra if it is a: 35mm, b:34mm, c:35.5mm, etc. I can tell you at the moment, from experience, that a 35.5mm adapter will not even fit inside the f-stop bezel. And from looking at it, I do not think a Series VI push on adapter will allow the bezel enough room to disengage the EV lock.

In the old days, I could take the camera down to the camera store and try several to find one that fit. These days I have to buy it off eBay and then eat it if it doesn't work.

But this is kind of off topic in this thread which is about the focusing problem that seems to be fairly common on Iskras.

To bring thing back on topic, as I was laying in bed waiting for the 87 meds I seem to be taking to knock me out last night, I got to thinking about that seemingly miraculous smoothing out of the focus on mine, I realized that it was probably just that I had loosened that one over tight screw. That was probably warping the front standard, and with the tension off of it the standard may have gone slowly back closer to its intended shape. Well, it beats the Brownies idea...

 

[VictorM.]

I found a Series 5 to Series 6 step up ring that fits securely. The thread pitch isn't quite right, but the adapter works quite well and allows the use of commonly available filters and hoods.

Like this: http://cgi.ebay.ca/STEP-UP-Camera-L...ultDomain_0&hash=item5d2dd2ff5d#ht_500wt_1156

 

[P C Headland]

Graywolf

What I've said about the series adapter rings IS correct - I actually tried them on my Iskra just to confirm before I wrote the reply.

The 35mm series VI ring I referred to in my post is a push on type. The series V to VI adapter is a screw on type.

 

[Ernst Dinkla]

One of the problems is a plethora of conflicting information on the web. For instance I have it on good authority that a Series VI retainer ring has a:32mm, b:33.5mm, c:34mm, etc threads.

A Series VI adapter will fit the Iskra if it is a: 35mm, b:34mm, c:35.5mm, etc. I can tell you at the moment, from experience, that a 35.5mm adapter will not even fit inside the f-stop bezel. And from looking at it, I do not think a Series VI push on adapter will allow the bezel enough room to disengage the EV lock.
.

The VI series adapter ring 1 13/32 - 35,5mm, clamps slightly bended inwards, fits nicely on the 33E (33x0.5mm thread) filter that of course protrudes about 2mm in front of the lens. I can push the adapter totally towards the lens and the f-stop bezel can still be reset against the T bezel for another EV value. Here it works like that for more than 5 years, of course it is possible that time had a hand in it too.

Ernst Dinkla

 

[graywolf]

Well, I have a Series V retainer, and 36.5mm push on adapter coming from the guy I bought the others from. He sorted through and found a retainer ring that was close to 33mm, and checked that the adapter fits the outside of the retainer. I want the push on because I have a square Series 6 hood I want to use.

The problem seems to be that things were not so precise back 50 years ago. On my Iskra it looks like a 35 or 35.5 push on would fit the outside of the filter ring, but they would never fit inside the bezel. I really do not want to order a filter from Russia for $30 shipped just to destroy it, either.

For those who want to know, standard US Series 5 rings are 33.5x0.7. He says he found one that is closer to 33mm. That should work as a jam fit. The seller is [SIZE=+1]macintoshcat; [/SIZE]He has gone out of his way to be helpful, all for a $4.95 sale. If this does not work, it is my problem, not his.

 

[Ernst Dinkla]

The nicest open air camera fair in The Netherlands is at the end of the summer in Doesburg. Old cosy town and a mile of booths at both sides of the streets. Mr Headland knows that fair but is too far away now. First time I bought the Iskra from some Ukranians for a fair price. Next time I found some 33E filters and a 33E flexible hood, 15 Euro at most I paid for them. The one taken apart had a nearby correction lens I guess, curved with no color, not usable on a rangefinder in practice. If that set is sold with the Iskra there will be a price paid for the total of hoods and filters I guess, given the common quests for an Iskra filter solution.

Ernst Dinkla

 

[graywolf]

Well, the Series 5 retainer and 36.5 adapter came today. Seem to do the trick. I will try to get some photos up over the weekend.

The focus continues to be smooth, and even, if still somewhat stiffer than I would like, nowhere near as stiff as it was when I got it however. No pictures to show from the Iskra, because I have been somewhat ill the last 3 weeks.