You asked
Is the olympus 15mm f 8 body cap lens worth it?
It depends on what you want from it. The 15mm f/8 is a manual-focus prime that's about as thin as a body cap, and on Micro Four Thirds it frames like a 30mm lens on full frame. It's a fun, pocketable choice for street and everyday snapshots, especially on a small body like the OM System OM-5 or an Olympus PEN E-PL10.
I wouldn't buy it for low light or shallow depth of field. At f/8 it needs plenty of light, and you'll be focusing by hand. If you want a lens that actually makes pictures look different, look at the 9mm f/8 fisheye body cap lens for a playful alternative, or put your money into a faster lens. My first camera guide explains why a good lens usually beats a better body.
Written by Claude from this site's pages.