I own a Helios 81-N 50mm/2 lens. It’s an absolute steal, you can pick one up for about 20-30 US dollars on ebay. It’s a russian lens but has a copy of the Nikon F-mount and as such will fit on any Nikon-camera. I had to modify mine a bit (with duct-tape!) so the aperture ring would line up with the aperture-feeler on my camera but that might be limited to my lens.
However, the reason to own one of these is it’s spectacularly interesting optics. It’s not a “good” lens as most would define it, it has some coma and a very busy and nervous bokeh, but I love it. I really love the bokeh which creates an almost painting-like effect when you hit the sweet spot for it. Also, the lens is actually insanely sharp! Last but not least, apart from it being cheap it’s very solidly built out of metal and glass; plus, it’s tiny and could qualify for the “pancake” badge.
This lens produces automatically very interesting photos of flowers and other things like it. I can’t really explain why, but whenever I want to make an artsy photo of a flower, this lens delivers the goods. It’s also great for casual portraits of people. I strongly recommend you find one on ebay or wherever. This photo was shot wide open at f2 and because the depth-of-field is so thin (I was at minimum focus-distance) it’s difficult to get your subject in that razor-thin slice of DOF. Somehow, I managed. Well, mostly managed. The top of the seed-pod is somewhat out of focus.
