These Helios' are renowned for theirs swirly bokeh, which makes their pictures very unique.
Many people love them and most of the are adaptable to be used on modern DSLRs.
From what I've noticed , they lack in contrast and sharpness wide open and there are also a flaring issue.
It is a M42 screw mount and you can use cheap adapter with chip to get focus confirm.
Please note some versions of Helios (44M-3, 44M-4, 44M-5, 44-M6 and 44M-7 can't be fitted on Canon's full frame cameras because they will most likely hit mirror when you focus them to infinity. I can't say for Nikons.
Uploaded: Dec 31, 2015