Nikon Ai-S Nikkor 35mm f/1.4 Disassembly – Trying to Repaint the Edges of the Front Elements

The Nikon Ai-S Nikkor 35mm f/1.4 is a fast, wide-angle prime for Nikon F-mount cameras. I serviced this one in September 2024. This post walks through the disassembly of the front group, step by step.

The job was to try to repaint the black paint on the edges of the lens elements. On many old lenses this black edge paint flakes off over time. When it is gone, light can bounce around inside the lens, which can lower contrast and add flare. In Japan this is called koba-ochi (edge paint loss).

This model is known for it: a great many copies of the Ai-S 35mm f/1.4 have edge paint loss.

Before: the white dashes around the edge

The listing said the lens looked very clean, and that no fungus or haze could be seen inside. When it arrived, though, I found edge paint loss. Looking in from the front, you can see a ring of short white dashes around the edge of the glass. That is bare glass where the black paint has come off.

Later, I looked at the listing photos again. In the photo looking in from the front, the same row of white dots was already there. So this problem can be spotted in photos too. When you buy a used lens, look at the photo taken from the front, and check for white dots or lines lined up around the edge of the glass.

1. Opening the front of the lens

On this lens only the front group needed to come apart, and getting to it is not difficult. There is a small set screw on the side of the front barrel. Loosen it first.

Then the parts at the front are loosened one by one.

Next comes the part that holds the front group. It has two small holes; with a two-pin tool in those holes I loosened it, and the front group came out.

2. Taking out the front group

Now the whole front group lifts out of the barrel. With it out, you can see the aperture blades deep inside the barrel.

3. Taking the elements out of the front group

The front group comes apart into two pieces.

Here is one of the elements still in its cell. Even from this angle, the white dashes are visible around the edge of the glass.

To lift an element out of its cell without touching the glass with my fingers, I used a small rubber suction cup.

4. Cleaning the edge

Before painting, the edge needs to be cleaned. For this I used lacquer thinner, a pointed wooden stick and tissue.

I used lacquer thinner to take off the old, flaking paint from the edge.

5. Painting the edge – the hard part

This was the hard part of the job. Honestly, it was a real struggle. The edge is narrow and curved, and no matter what I did, I could not get the paint on cleanly. By the end, my gloves were smudged with black.

Then the edge was painted black again. What to paint it with was the hard part. I started with bottled Japanese ink (bokuju). I had read that bottled ink tends to bead up on glass and not stay, so I also bought an inkstone, a brush and an ink stick, ground my own ink and painted with that. I tried car touch-up paint as well. In the end, what I settled on was water-based paint, the kind made for painting pictures.

How to paint it mattered just as much. Painting freehand with a brush, I could not get a clean line at all. What finally worked was an electric turntable, the kind used to spin products in videos. I fixed the element on top and painted it while it spun round and round, like a potter’s wheel.

One coat was never the end of it. I tried one way of painting, wiped it off, and tried a different way, again and again. Altogether, this lens took me about five days of work.

6. Close, but not quite

These photos are from one of those days, late at night.

About a month later, I photographed the lens again, fully assembled.

Looking in from the front, the bright white flaking I saw at the start was gone. The repainting made a big difference. But it did not go all the way back. A faint trace was still left around the edge: depending on how the light hits it, you can still see small dots, and the colour of the edge looks slightly different.

So it got much better, but it was not perfect. Because of that faint trace, it did not reach the standard I set for the lenses I send overseas, so I did not list this one for buyers abroad. Instead, I let it go here in Japan.

Not every repair ends exactly the way you hope, and I wanted to write about this one honestly. Two things I took from it:

First, on this lens, edge paint loss is very hard to fully fix by repainting. A thin, curved edge is not easy to paint by hand, and it is hard to make it look exactly like it did from the factory.

Second, it is better to find it before you buy. Look at the photo taken from the front, and check the edge of the glass for white dots or lines in a row. In this case the sign was there in the listing photo all along.
Thank you very much for reading.

---