Obscura

The Lensbaby Obscura is a lens...not really a lens though because you can't focus it!  Because it's hard to explain and especially if you're not knowledgable of the history of lenses and photography I'll let Lensbaby explain!   Here's a quote from their website: "The Lensbaby Obscura comes in two versions. A 50mm Pinhole/Zone Plate/Pinhole Sieve optic - for our Optic Swap System and a standalone 16mm Pinhole/Zone Plate/Pinhole Sieve pancake lens for mirrorless cameras.  Lensbaby Obscura envelopes photographer and lens in an elegant dance between light and dark while bringing unique flare and image artifacts that aren’t possible to achieve in-camera with any standard camera lens. 

The 50mm Obscura* has f-stops and minimum focusing distances  of 

Zone Plate: f/32---Zone Plate: 10" (0.27m)
Pinhole Sieve:--- f/64 Pinhole Sieve: 9" (0.24m)
Pinhole: f/161---Pinhole: 0.04" (0.001m)

Lensbaby also has a 16mm pancake lens for micro four thirds cameras.*

These choices may no longer available at Lensbaby.com but you might find them at other retailers and used.  

Personally, I found this choice to be challenging and not easy to adapt to my work flow.  If you're looking for others that use it well, check out  the Lensbaby Unplugged group on Facebook and search #obscura or #lensbabyobscura