Shaving a Nikon 10.5/2.8 Fish-eye Lens
Thomas K Sharpless, 12 December 2013
I make no claim to originality; lots of people have done this, and I have taken the advice and example of many of them. The only unusual thing is that I left a small “petal” at the center of each of the original large petals, to hold the lens cap slightly away from the glass surface.
Since I have a small machine shop and none too steady hands, I have used a little jeweler's circular saw mounted in a milling machine to do most of the cutting, with the lens set in a simple fixture that lets it turn smoothly. Step by step....
Put on the rear lens cap.
Set the focus ring at infinity, so the front of the lens is as deep as possible in the hood, and tape it there (I actually forgot the tape and was lucky the lens did not extend while I was working on it).
Slip a cylinder of paper into the crack between the lens and hood, fold it down in the middle and tape it. This protects the lens surface during the operation.
Clamp a pair of vee blocks, raised on spacers, to the mill bed to make a fixture that lets the lens turn without binding and without wobbling.
On a strip of paper wrapped around the lens, mark the widths of the large and small petals (to bottom of notch) around a common center. Use this to mark the center and small width on the large petals with a pencil.
Cut off the tops of the large petals to a depth about 2mm below the tops of the small ones. Turn lens by hand, with a finger on top of lens center. Take several shallow cuts, moving the bed about 0.3mm (.015”) between cuts.
Cut off the small petals just below the bottoms of the notches (cut surface is about 1 mm below bottom of notch). Run the center of the saw out to the marks representing the small petal widths.
Using a fine keyhole saw and a matte knife, trim the new petals at an oblique angle so that they are a bit narrower than the marked width, and only a little of the circular saw cut remains visible.
With the matte knife and a jeweler's “riffler” file, deburr the cut edges and shape and smooth the little petals.
Wash your hands; blow away chips as much as possible; pull out protective paper; blow and wipe lens clean.
Here is the finished product, on a Novoflex NEX-NIK adapter, ready for the Sony A7r that hasn't arrived yet....