csisfun said:
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
