The Russian Helios 44M lens was supplied on most of the Zenit 35 mm SLR cameras produced and, since there were literally millions made, is readily available for a relatively low price. Being M42 screw mount means it's possible to adapt it to many mirror-less and DSLR cameras.
I have a couple of examples, both or which are the 44M version which has the aperture actuation pin in the lens mount to allow the lens to be stopped down at the moment the shutter is fired. Of course when used on a digital camera with an M42 adaptor the pin is pushed in and not used anyway.
The basic design of the Helios 44 was a copy of the Carl Zeiss Biotar 58 mm ƒ/2, a fantastic lens but pretty expensive to acquire. The Helios on the other hand can be found for only a few pounds, often attached to a Zenit SLR (which is the way I bought the two Helios 44's that I own). Of course, being a copy of a great lens doesn't mean it's going to also be great - as with many soviet lenses it all comes down to how close a copy you get. The quality control with these lenses can sometimes leave a lot to be desired, so it's a bit hit-and-miss as to the quality of lens you get.
The focal length is a quite long 58mm which, when the crop factor of the APS-C sensor is taken into account, makes it a useful portrait length of 87 mm on the NEX 6 mirrorless camera I used to take these sample images. The aperture has a range of f/2 to f/16 and uses 8 blades which are arranged to give an almost circular profile.
Helios 44M Sample Photos
The gallery below shows some sample images using a Helios 44M fitted to my Sony NEX 6 mirrorless camera. Most of these pictures were taken with the aperture opened up because this is the way the lens is typically used, and it displays the most characteristic feature of the Helios 44 - the swirly background. This is a technique most often used in portraits, which makes this a very useful lens to have in your collection. There are also a few shots with the lens stopped down to show that it is also capable of some pretty good general purpose pictures.
Helios 44M Sample Video
Another use of the lens is for videographers of course, which is something I have only limited experience with, but I have taken a sample video using my version of the lens which has no click stops in the aperture ring. This allowed me to slowly change the aperture as the video was being recorded and subtly change the background blur during the course of the video, which is quite a nice effect.
Helios 44M Results
I think the Helios 44 is a good general purpose lens but really comes into its own when used in situations when you want a blurry background, typically for portraits. However, I think its use needs to be somewhat limited because although the swirlyness of the background is a nice effect, it can get overpowering if overused.
Considering the price of the lens - typically between £15 and £30 to buy one, normally with a free zenit camera thrown in, this is the sort of lens which most photographers should own. As a bonus, they are quite easy lenses to repair if they go wrong.