Photographers often like to speak about bokeh, the ability of a lens to render the out of focus area. Especially prime lenses with a fixed focal length and a wider maximum aperture are able to render a nice blurred background.
Flee markets are very nice. You can find old photo gear for a bargain. I wasn’t even looking for a new lens but when I saw the Pentax Super Takumar 300/4 in the multi coated version with M42 mount for a quite reasonable price, I had to get it. Olympus just released the similar m.Zuiko Pro 300/4 which is probably the best lens for Micro Four Thirds but for my needs out of reach. Why not try a much more cheaper old vintage lens option with an M42 adapter on my camera? It certainly is not as sharp as the brand new m.Zuiko 300/4 and you have to focus manually but for occasionally use this might fit very well my pocket.