If you place the lens immediately in front of the SLR mount and, moving it back and forth, still see no focused image there is either an element missing, or one that is reversed, or a different element in the place of another. This is a shame, and possibly a sham as well, Darkosaric. If the lens were good you WOULD see a sharp image fleet into and out of focus, depending upon how closely you are holding it to the SLR. Even if it were heavily scratched you would see a sharp (but very uncontrasty) image. I wish I could cry with you. - David Lyga
Not sure using a SLR does the trick as a screw mount Leica has a shorter register (28.80mm), unless you can bury the lens inside the SLR camera body...
I'd try it in on a 35mm enlarger, see if it will focus. If it won't then start looking to see if someones tampered with the elements.
Hi - looks like it is focussed well before infinity. Is your Leica one with an opening back panel? If so you can put a ground glass against the film rails, set the camera on 'B' with the shutter open and experiment with focussing on different objects at differing distances to see:
1) Whether you can focus on anything at all,
2) What point on the scale currently relates to infinity.
If you can't focus on anything at all, it may be that someone has had the lens apart and lost a spacer or put one of the elements in back-to-front.
If you can focus on something then previous posters suggestions about unscrewing the focus mount and moving on to another thread may be the answer.
If you can't mount a glass screen on the camera, try cutting a card tube to 28.8mm (focal distance of the Leica screw thread body), placing the lens in the front and a ground glass on the back and doing the same experiment. This is a rough and ready way of checking the lens out :>)
Dali, the register does not matter: you are holding the lens and moving it back and forth from the empty mount. You would cover all bases here.
Ian, the enlarger is also a good idea, especially because the Summar has a 39mm mount and would screw into the enlarger easily. - David Lyga
The fact that the mount is empty does not change the fact that you have to place the Summar at the register distance to focus at infinity and some millimeters longer to focus at shorter distance. As a SLR is thicker than a Leica LTM, I doubt your the experiment would be useful.
At the opposite, Kiev88user preconisation to use a ground glass at 28.80mm distance makes sense. Instead of using a cardbord, you can use some macro rings to achieve the 28.80mm distance (this is how I check the real working distance of my old and non-standard russian lenses).
Perhaps someone in the past worked on it and either swapped the elements with another lens (possibly not even a Summar). Or as someone else said, an element was reinstalled reverse -- don't know if that's possible with this lens, as I'm not familiar with the construction.
I agree with kiev88user. You cannot focus that lens through an SLR.
We can see the lens will project an image from the posted scans. The best method is what kiev suggests, ground glass at the film plane & observe focus.
The Summar and Elmar do not have a focusing helical. it's a continuous thread.
It may be that the focus is off by being screwed in too far or not far enough. The infinity stop is a simple post screwed in place. Remove it and you can check on the GG as the lens is moved beyond it's normal limits.
If it unscrews, no problem, just screw it back in again. If it won't get a sharp image within it's range it's time to consider mis-assembly.
As others have said the lens has most likely been disassembled and re-assembled wrong. To the person who claims the Summar is the worst lens...he is totally wrong. This is a fine lens still capable of producing excellent quality images. I still use 2 of them..
To clarify: you CAN focus that lens through an SLR. Not for picture taking but you can focus merely to see if that lens is capable of sharpness. You hold the lens in front of the mount and look through the viewfinder. Then you slowly move the lens back and forth until you get a sharp image. This sharpness will be fleeting and transitory but it will be there. Register distance does not matter here as you are not affixing the lens to the mount, merely seeing if the lens is CAPABLE of sharpness. Yes, even with an enlarging lens you can do this. - David Lyga