Modification of pre ai Nikon lenses for use on some DSLR's

Hamish Gill

Tech Support (and Marketing)
This is a Nikkor 2.8 45mm GN lens:


This particular one has the Nippon Kogaku branding on it. It was designed to work with Nikon cameras like the 'F' and 'F2'. It has an aperture coupling prong adjacent to 5.6 on the aperture scale - i believe some people call it "bunny ears". Whatever you call it, its that little silver thing sticking out the side of the lens.
Older pre-ai cameras had a little pin that this engaged with, this allowed the meter to give you a read out that differed when changing the aperture without having to actually stop down the lens.

Below you can see my Nikon f2, and if you look closely at the bottom of the head you can see the little pin.


And here you can see that the prong engaged with the pin.


So this is how my 45mm lens works with the cameras of its generation, unfortunately this is not how a d3 works!

Modern lenses and d3s talk to each other with a lot of electronics that I don't fully understand, all I know is that with my camera in aperture priority or manual mode, I twizzle the dial under my forefinger and it changes the aperture that the camera will stop down to when i press the shutter button. Clever stuff! Not quite as satisfying as the older mechanical way of doing it but clever non the less.

This all said, all is not lost in attaching older manual lenses to a d3, as those clever folks at Nikon have, on their higher spec models at least, provided a little lever that ai/ais lenses can engage with. This means that as long as you provide the camera with the aperture of the lens you wish to attach, the camera can meter the exposure at whatever aperture you choose to set the lens too.

Apart from the fact that you don't have to tell the camera the max aperture of the lens, this is the same system that, as far as i know, was used on all ai/ais cameras and as such here is a picture of an ais lens attached to a Nikon FA. You can see the part of the lens that juts out adjacent to f16. This pushes the spring loaded lever on the camera and tells it how to meter depending on what aperture you set the lens to .


Its basically a neater and less clunky version of what came before .
My problem is that my pre-ai lens (obviously) pre dates this system and so I need to modify my lens in some way so that it can push this little lever...

...and this is how i did it

First remove the coupling prongs as they, on a 45mm pancake lens, interfere with with the little lever.


Keep these bits safe as you will be able to reattach them should you wish to use the lens on a camera where they are required.

Now it is nessasary to file a slot in the rim of the lens for it to engage to the lever
By looking at whereabouts the part of the lens that engages with the lever on another 2.8 lens is, I can determine where I need to file. In this case it is adjacent to f11.

Please be aware that this is not the case on all lenses, if you are trying to adapt a 1.2 lens for example, you would need to file a slot between 5.6 and 8 but I would seriously recommend looking at an ai/ais equivalent to find the exact spot.

Here is the slot I filed.


And here it is engaged to the lever on a d300.


When mounting a lens moified in this way you will need to stop the lens down to its minimum aperture to mount the lens on the camera!

I now have a fully functional 45mm mf lens for my d3 and d300.

And here are some (fairly dull) photos I took with it on my d3. I will put some better ones up when I get a chance. You can at least see that it works!



I'm no expert at this sort of thing so it is fairly easily done. That said, I take no responsibility if you follow my instructions and balls it up. You do this at your own risk

And for anyone who may quible with my desision to hack apart a nippon kogaku branded lens, its a damn slight cheaper than the 45mm 'p' lens and at least this way I get to appreciate a old bit of glass with the ease of use of putting it on my digital cameras. And if i want to use it on my f or f2 i can still reattach the coupling prong!

I wrote this for my blog a couple of years ago, so sorry the images are a little small... i have since reatched the bunny ears and the lens is back on the nikon F ... just as proof i haven't caused any damage that would prevent it being used on the kit it should be used ....



here is a link to KR's useful nikon lens compatibility chart for reference