Split-screen out of focus - wide angle lens

[raff]

Hi,

I am new to analog photography and, as a beginner, I've encountered some issues; insights would be highly appreciated.

Recently, I received a Zenit 122 with a Helios 44. Everything works perfectly fine.
The camera uses a split-screen as a focus assistance. The split-screen is perfectly aligned at all given distances (close to infinity focus).

Recently, I've acquired a MC Mir-20M lens, which is a wide-angle lens and, according to the camera manual, should be compatible to my camera. The lens is in very good condition, the aperture clicks at every mark and the focus ring moves smoothly. Also, there are no abrasions, thus, it hasn't been used too often. However, the split-screen seems to be out of focus at given distances:
- To get an aligned screen at e.g. 2 meters, I need to set the focus to about 4 meters.
- Infinity focus does not get perfectly aligned; it would have to go a little bit further.

What I'm wondering, is, if there is a problem with the lens, or if the components are not sensitive enough. Is this usual? It works fine with one lens, but not with another lens.

I could take some pictures at given distances and develop a film. However, that takes a while and I need to contact the seller timely if anything's wrong. Also, a canon adapter takes a while to ship.

Thanks,
raff

 

[halfaman]

Normally it should be a problem of the lens and it is usually a cheap repair (infinity calibration).

 

[AgX]

Someone hampered with the calibration of the focusing barrel by taking it off and setting in on again wrongly. It would be a basic calibration.
However one should ask why there was any manipulation at all. Is or was something else wrong with the lens?

Maybe though someone knowledgable on this lens got an idea how such focus missetting could have happened without manipulation.

 

[neilt3]

It sounds to me that your saying that when you focus in the viewfinder , the distance shown on the focus scale does not agree with the distance you have really focussed at .
Does the lens focus correctly for the full range , ie , the picture has sharp focus when when focussed at infinity in the viewfinder even if the focus scale says 10 feet ?
When you focus at something 5 feet away , the scale says 10 feet ?

If the lens focusses for all the range correctly and just the focus scale is out , then you don't have to worry .
But this could be an issue if you scale focus .
I.e , camera on a tripod , you want to focus at something 10' away and set the focus to suite .

You say in your post " Also, a canon adapter takes a while to ship" .

Are you using this lens via an adapter on a Canon camera ?

If so , and if the adapter is slightly too thick it will act as a very short extension tube .
With a longer lens you won't notice , with a wideangle lens it makes a distance .
It's also possible to lose infinity focus with very short lenses .

 

[raff]

Thanks for your inputs.

@AgX: there is nothing else wrong with the lens, as far as I know.

@neilt3: exactly, focusing with the viefinder does not agree with the distance mark on the lens.
when I focus at something 5 feet away, the scale says 10 feet.
when I try to focus at infinity, I do not receive an aligned split-screen, even though the scale says inifinity (the split-screen says indicates less than infinity focus).
I am currently using the lens with my Zenit, no adapter.

 

[neilt3]

I agree with the others then , it just needs adjusting .
It's normally a simple job to do yourself , if your happy doing that sort of thing .
Do a search on adjusting this lens first though .

I don't know how much a repair shop would charge to do this , but would be worth checking first .
If your not happy , and the seller will take a return , that's your other option .

 

[raff]

If it's an easy fix, I don't really mind, thanks!

The seller has two more lenses (in worse condition though) of the same model and offered me to check those out, too, and pick one.

 

[ic-racer]

First off, I'd ignore the split image aid with a 20mm or wider.
To see if the lens is collimated (ie the infinity stop is at the right spot) you need to use something like a microscope slide with semi-transparent tape to see how the lens focuses a distant object (horizon or something).
If the infinity stop allows it to focus beyond infinity, that is not too bad, as many autofocus lenses share that same trait when used as manual focus. If the lens won't make it to infinity, it certainly needs re-collimation.

 

[raff]

Could you elaborate on how the set up looks like? What do I need the tape for and how far away do I place the slide?
I‘m interested to try that.

Thanks!