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A more secure lens cap for the Nikon 16mm fisheye


The old classic cameras (and a few modern "retro" designs) come with slip-on lens caps. I've lost a few of these expensive caps that rely solely on friction to stay on, and I'm therefore not a big fan of the caps that come with the Nikon fisheyes.

The old manual-focus Nikon 16mm AIS fisheye is a bit smaller than the newer 10.5mm DX lens (and the 16mm AF).  The slip-on cap for the newer lens is too big for the old 16mm lens. As a replacement cap for the older lens, you will need to paste some adhesive tape inside to get a tighter fit.  I was not satisfied with this solution (hence this DIY project).

This page is about a clip-on cap that attaches securely to the upper and lower petals of the built-in hood of the fisheye lens. 

In esssence, a custom-made ring is bonded to back of a standard 58mm Nikon lens cap.



 The MakerBot Replicator 3D printer is used to create two rings out of black ABS plastic.


* Note:- Following this release, my friendly hobby shop supplier has advised me that the custom part could have been fabricated as a single piece ( I'm a newbie to CAD and 3D printing! )See the one-piece version below......much simpler solution!




Completed plastic rings.

The taller ring has an inner diameter of 62mm, height of 19.5mm and thickness 2.5mm.

The smaller ring just fits inside the larger ring. It is 7mm tall and 2mm thick.






The two rings are separated from support base






Two small arcs are cut off from the smaller ring to make the flanges.






The first arc is mounted inside the larger ring.






Detail of flange.






The second flange is added.






Solvent grade acetone is used for bonding the ABS plastic.




The assembly is turned on a mini lathe, to smooth out the faceted surfaces of the ring.






Final polish is achieved with fine grit sandpaper.




A much easier approach......

(updated on 1 Oct 2012)

Mk II design is printed directly as one piece, bypassing all the above steps.


(updated on 1 Oct 2012)

Google SketchUp design for Mk II version

Download this 3D design to print your own ring.

Note: - This is for the 16mm AIS MF lens. For the 16mm AF or the 10.5mm DX lenses please increase the overall scale by 2%.






Test mounting onto fisheye lens.

The flanges fit in between the petals of the built-in lens hood.






An off-the-shelf 58mm lens cap is bonded to the flanges with acetone.




The pinch action is preserved, inside the ring.

The two jaws clip onto the built-in hood.






Completed cap attaches securely to the built-in hood.





Rokinon (Samyang) 7.5mm fisheye for micro 4/3.

The lens cap for this Korean-made lens was the inspiration for the above design.

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