Thank you Jakov ! I am glad you love them.
Did you use extension tubes also?
No extension tube, but the mount adapter M42 to F mount is itself an extension since the lens is kept away from the body.
Even if you hold the lens against the body mount, you don't get sharp infinity. (infinity is blurry at full aperture)
By the way, I can't get infinity with this lens on the Sony Next nether, which I thought it was designated to accept any M42 mount lenses.
However, if I slow down its aperture, eventually I can hardly see infinity, which means the M42/Sony adapter is 1 or 2mm too thick.