Hey, u ever see a cell-focusing SLR lens? Nah? Well now you have. I'm assuming that this was the absolute cheapest lens that it was possible to make, dispensing with the multiple helicoids of a unit focusing lens for a single moving front element that kind of partially unscrews to focus. Image quality is wonderfully soft wide open, especially at closer range. Please do not buy this as a standard 50mm lens and expect it to be "good," because it is not "good." It is, however, possibly great. If you enjoy wacky lenses, this should be in your camera bag. Standard K mount for Pentax or Ricoh cameras.