Recently I bought the smallest digital Interchangeable Camera System from Craigslist. It´s called Q and it is made by Pentax (now Ricoh). The Pentax Q System consists of several Interchangeable Lenses and one of them is particularity interesting because it is very very slim, just 6.9 mm. It is the Pentax Q 07 Body Cap Lens aka the “Mount Shield Lens”. Body Cap Lenses have no focus mechanism and typically no aperture to choose from. What you gain from this minimalistic Zen-Design is the opportunity for real Snapshot Photography! This lens is by far not the only model around. Read on and compare available Body Cap Lenses and Pinhole Lens Caps for interchangeable Camera mounts…

There are two different types of fixed distance (lens) designs:

• Body Cap Lens has usually a plastic lens element integrated.
  • Advantages
    • Light and durable
    • Cheap
    • Fixed Focus
    • Quick and fun to use
  • Drawbacks
    • Less sharp compared to glass lenses
    • No aperture control (with exceptions)
    • Resulting images look often soft in the corners
• Pinhole Lens Cap has no lens element at all, there is only a tiny hole in a cap.
  • Advantages
    • The lightest possible (lens)
    • Cheaper
    • Fixed Focus
    • Huge Depth of Field
  • Drawbacks
    • Very long exposure times! (Hand held shooting not recommended)
    • Almost no preview (live-view) possible because it´s too dark
    • Resulting images look overall soft, very soft!

If you notice that a information about a lens is missing, please let me know in a comment below!