Zorki 4 lens registration distance woes...

[csisfun]

Hello,

My Zorki 4 has a problem. It seems that the lens registration distance (film plane to lens mount distance) is out by 1mm or so. I have removed all the shims, however, it's still not 28.8mm yet. Does anyone have any idea how else I can get closer?

It's such a beautiful, solid and sexy camera that I just have to make it work... help?

 

[fidget]

That's a long way off, how are you measuring it? (thinking of the sprung pressure plate that gave me problems when measuring)

BTW, welcome.

Dave...

 

[csisfun]

Hello fidget. I'm measuring it down it's throat - I'm sticking a ruler in from the lens mount down to the the spring pressure plate, in bulb mode. True, I'm having problems actually measuring the distance, as I don't know where to put my eye. I tried looking perpendicularly, but it doesn't look accurate...

I tried the focus screen in the back method, An object look all in focus after the 1.5 mark. They probably aren't out of focus, but I cannot detect the nuances. With a magnifying glass, they still look the same!

Save me!!

 

[Spyderman]

You need to get a proper caliper to measure it precisely enough.

(need not be digital... since we're measuring a FSU camera)

Don't trust a ruler... The register distance is too important to trust a ruler.

 

[fidget]

I agree with Spyderman, you can't use a ruler for this. You must check/adjust the measurement to +/- 0.02mm. Can you borrow a set of vernier calipers as in Spydermans picture? (they were for sale in the UK at Aldi recently, cheap).
Do your pictures show a problem?----or now that it's apart, did your pictures show a problem in focus?
Dave..

 

[ZorkiKat]

Hello,

My Zorki 4 has a problem. It seems that the lens registration distance (film plane to lens mount distance) is out by 1mm or so. I have removed all the shims, however, it's still not 28.8mm yet. Does anyone have any idea how else I can get closer?

It's such a beautiful, solid and sexy camera that I just have to make it work... help?

I'll be the nasty one and say that the defect is in the operator, and not in the instrument.

First, how were you able to determine that the lens register was defective? Was it focusing badly when you first got it? For any focus error then assumed, was it based on what was seen in the rangefinder, or was this observed in actual photos seen on prints or magnified negatives?

Second, as the others have already mentioned, measuring the focus register/working distance should be made with a very accurate (precise down to 0.02mm) caliper. No other device or a similar one with less precision will do. Rulers included- at best, they'd be able to give you a milimetre's worth of values, if these would be accurate enough.

Then, when using a probe to measure the distances, make sure that this probe doesn't bear down on the pressure plate. A slight shove is enough to make a 0.5mm discrepancy. Measuring the working distance/register is the only way to go with a bottom-loading camera.

But with one whose back opens like the Zorki-4, there are ways around. First, a simple grounglass screen (rough surface should lie exactly on the inner rails) used with a proven lens will show if the camera is properly adjusted or not. Or if you must insist on using a caliper, the back can be removed, the groundglass pressed against the focal plane, and let the probe drop on the glass surface facing the lens mount. At least, glass pressed from behind is more rigid than a pressure plate sitting on two delicate springs.

....I have removed all the shims, however, it's still not 28.8mm yet.....I tried the focus screen in the back method, An object look all in focus after the 1.5 mark. They probably aren't out of focus, but I cannot detect the nuances. With a magnifying glass, they still look the same!

And what was the reason for removing the shims? Zorki-4 came from a time when the materials and methods used for making cameras were good enough to produce machines with more uniform specs, and required less adjusment.
Zorki-4, with cast bodies and crates fixed to the shell, are likely found with more accurate registers than a bottom loading Zorki-1 with a stamped body shell. Unless the camera was given a stock lens mount whose thickness wasn't measured for the body, the lens mount would usually be installed at the proper distance with just a shim (or often, a partial one) or two.

Removing the shims and finding that your lens now focuses at infinity at its 1.5metre mark only INDICATES that you've effectively shortened the lens mount to focal register/distance. With its mount sitting closer to the film plane than as needed, the lens now has to be racked out (as it is when set to 1.5 metres) to achieve infinity focus.


Note too, that focusing problems seen in pictures are not necessarily a lens register problem. The rangefinders of Zorki and FED have to be adjusted meticulously at BOTH infinity and minimum focus settings.


Jay

 

[pshinkaw]

I agree with Jay:

When testing out a Soviet era camera, it is important to follow a set routine of testing before attempting adjustments. Just removing stuff can cause more consequential problems then originally existed.

On flange to film distance: I use an aluminum 'L" channel with a hole drilled in it to square my dial caliper up to the lens mount. Measuring diagonally down a lens throat is a waste of time.

When you are dealing with +/- 0.02mm, there isn't much room for variation in methods.

I also put a piece of film in the gate, over the pressure plate to prevent scratching the plate. It also helps in ascertaining when the plate is in contact with the measuring probe since the reflectance changes when the probe touches the film. I measure five different locations, and toss out the highest and lowest values. I then average the remaining three. However, if two or more of the measurements are way out, high or low, I take more measurements in the area on the chance that one side or the other is significantly different from the other. Essentially I segment the film area and measure each part separately.

-Paul

 

[csisfun]

Certainly I can tell that my pictures are out of focus when

1. 4 rolls of film say the same thing
2. A ground glass shows that an object 1.5m away focuses best at 4m.

How did I know that the lens register was off?
1. Adding more shims exacerbated the problem.

I think it's time to send the camera in for repair... or buy a Bessa! I loved this Zorki, but it just doesn't do its job well...

 

[Spyderman]

The fun with FSU cameras is not just using them, but also that you first have to adjust, calibrate, CLA... etc.

Don't give up.

Try to remove the shell and you'll see the inner parts where the shutter is located. Then it is possible to remove the front part of this (the lens mount is screwed to this part) - it comes off as a plate. Maybe this is bent... or you could bend it slightly towards the film to decrease the flange to film distance.

 

[ZorkiKat]

Certainly I can tell that my pictures are out of focus when

1. 4 rolls of film say the same thing
2. A ground glass shows that an object 1.5m away focuses best at 4m.

How did I know that the lens register was off?
1. Adding more shims exacerbated the problem.

I think it's time to send the camera in for repair... or buy a Bessa! I loved this Zorki, but it just doesn't do its job well...

Where was the Zorki from? Any idea of its history? You should be able to iron out the problems IF you IDENTIFY the variables first.

There's a possibility that the lens mount was changed or replaced by a mount from another camera. That's one plausible explanation why your Zorki is behaving this way. Assuming that is, if your lens is faultless.

Have you tested your camera -before you altered its specs- with another lens to see if it was indeed the one at fault? Lenses can also be off, especially if tampered with, and give erroneous focusing similar to what you found. If the lens was at fault, using this on the Bessa will give you the same blurry pictures.

Give the Zorki another calibration, using proper measuring tools. Then once you're certain that it's at 28,8mm, fit a proven LTM lens on it (if you've got something like a good old Summitar) to make sure that any error isn't due to the lens. You should be able to see a sharp image of a distant object on the screen with the lens set at infinity.

The next step to do is to calibrate the camera's rangefinder for BOTH infinity and 1 metre focus.

 

[csisfun]

No idea of it's history. It was made in 1968. I bought it in China.

Both my J12 and I26 face the same problems, before and after. I really think I'm gonna send it in for a CLA, and if it's too expensive, I'll just keep it as a display piece.

 

[ZorkiKat]

No idea of it's history. It was made in 1968. I bought it in China.

Both my J12 and I26 face the same problems, before and after. I really think I'm gonna send it in for a CLA, and if it's too expensive, I'll just keep it as a display piece.

Getting another Zorki-4 may be a more economical alternative to having your present one actually repaired.

It must be the lens mount. I've encountered something similar in the past, with a Zorki 2C. Its lens mount flange was too "high" and no amount of shim removal would put it within specs. The Zorki-2C is too rigid, like the Zorki-4 chassis, to be distorted. It turned out that it had a lens mount from another Zorki. Replacing it with a spare mount from a scrapped camera was able to cure the problem. The questionable mount, by its appearance and thickness, looks to have come from a Zorki-4k. The 2C had been tampered with and given a smart-looking but out of spec lens mount to make it more saleable.

Jay