Ai Conversion of an old 5cm f2 Nikkor-S

[the solitaire]

The easiest way to convert this old Nikkor is to remove the rabbit ears and glue a small cam at the f11 position. Done.

I wanted a solution that was somewhat more reversible so I came up with this:



Unfortunately my 20mm f3,5 Nikkor-UD was already modified with a glued on cam when I bought it, otherwise I'd make a 2nd one of these

[longknives]

Nicely done, a much better mod than using glue.

[richardHaw]

what you have looks neater than mine

1st pic is with my 50mm f/2

2nd pic shows how I make a pattern using acrylic

3rd pic is on the 2.8cm f/3.5

your idea is better because the angle bar actually is more rigid than the hammered sheet aluminium that I am using

[the solitaire]

Richard, the silly thing is this. I only had a large piece (50cm) of 90 degree angled aluminium available. The material was far too thick so I had to file a lot of the material off (reduce overall thickness of the material by half) which was more work then would have been required. All in all it is quite a solid piece however, so I'm quite happy with the result (for now). I used needle nose pliers to bend the bar in shape so it fits snug on the aperture ring of the lens.

[Matthew Currie]

Aside from the earliest Nikkors,  a number of pre-AI Vivitars also lack the skirt depth needed to mill.  I wanted to convert my old 20 to AI but still needed to use it on the F, and this is what worked on it.  The material is relatively thin copper, and very easily worked.  It's thick enough to engage the AI tab but thin enough to go under the rabbit ears.

[the solitaire]

Matthew, that is another nice solution. With the 5cm lens and the 20mm f3,5 Nikkor-UD you would have to bend the tab in the opposite direction because the skirt is deep enough to go under the Ai tab, but it is not thick enough that milling would make a difference. Bending your copper strip in the opposite direction (0,5mm thick?) should do the trick as well.

[Matthew Currie]

Matthew, that is another nice solution. With the 5cm lens and the 20mm f3,5 Nikkor-UD you would have to bend the tab in the opposite direction because the skirt is deep enough to go under the Ai tab, but it is not thick enough that milling would make a difference. Bending your copper strip in the opposite direction (0,5mm thick?) should do the trick as well.

I see what you mean.  I have the old style 28/3.5 and its ring  clears the AI tab but the rabbit ears do not, so you definitely can't do what I did on the Vivitar, and you won't be able to keep the rabbit ears.  Clearance for anything is very tight.

[the solitaire]

You can actually keep the rabbit ears. You just have to shave a bit off them. Just about up to the holes for the screws actually. The heads of the screws also need to be shaved on one side to make the Ai tab fit past them.

[Matthew Currie]

You can actually keep the rabbit ears. You just have to shave a bit off them. Just about up to the holes for the screws actually. The heads of the screws also need to be shaved on one side to make the Ai tab fit past them.

  I've done the regular milling operation on a couple of newer pre-AI lenses like the one you show.  Looking at my older one, it looks as if one could mill only the rabbit ears and leave the aperture ring.  But to meter on AI you'd still need something like the tab you and Richard Haw show earlier, which doesn't look as if it would be comfortable with rabbit ears. 

Fortunately, my old 28 sits fine on a D3200 as is anyway, and I just stopped down on the F3 and 4, but never much cared for it in full frame anyway.   But it's also a beat up bargain bin special, so if I ever need to make it AI, I may take the drill to it.

[Hugh_3170]

Buddy, Richard, Mathew et al:  nice work guys & thanks for sharing. 

It is good to see these old lenses getting a fresh lease on life as a result of some simple metalwork and personal efforts.  One wonders what unloved oldies that are out there sitting in cupboards just waiting to be liberated by practical folks such as yourselves.

Another option for those with a hobby lathe is to turn up a thin ring that can be dimensioned and profiled so that the notches can be cut out for the aperture follower tabs of Ai cameras.  This ring can then be pressed onto to the rear/trailing edge of the aperture ring.  Would work best on non-Nikkor lenses with reduced diameter & width of aperture rings such as the early Vivitars and the like. Alternatively such a ring could be cut into short segments and such segments then used to create the Ai tabs and the existing screw holes used for the rabbits ears used to then fix them to the aperture ring.  Getting fancy, I will concede.

[richardHaw]

i have a surprise project for everybody but i just do not have the time for that now.

[the solitaire]

Buddy, Richard, Mathew et al:  nice work guys & thanks for sharing. 

It is good to see these old lenses getting a fresh lease on life as a result of some simple metalwork and personal efforts.  One wonders what unloved oldies that are out there sitting in cupboards just waiting to be liberated by practical folks such as yourselves.

Another option for those with a hobby lathe is to turn up a thin ring that can be dimensioned and profiled so that the notches can be cut out for the aperture follower tabs of Ai cameras.  This ring can then be pressed onto to the rear/trailing edge of the aperture ring.  Would work best on non-Nikkor lenses with reduced diameter & width of aperture rings such as the early Vivitars and the like. Alternatively such a ring could be cut into short segments and such segments then used to create the Ai tabs and the existing screw holes used for the rabbits ears used to then fix them to the aperture ring.  Getting fancy, I will concede.

If only Nikon stuck to a fixed diameter on their aperture rings, but alas, it seems every different focal length and sometimes even cosmetically updated versions of lenses uses a different diameter.

[Hugh_3170]

So true.  A good / bad example is the factory Ai conversion rings produced for the 43-86mm f/3.5 zoom.  Nikon offered three such rings, and depending on the Serial Number of the lens being converted this determined what was the "correct" conversion ring.  They all had different cosmetics, although at a pinch they could sometimes be mechanically interchanged.  There are a few other such examples of this in respect of the conversion rings. 

With the affordability of modern CNC machining equipment, it is a pity that Nikon or a third party don't start making these conversion rings again.

If only Nikon stuck to a fixed diameter on their aperture rings, but alas, it seems every different focal length and sometimes even cosmetically updated versions of lenses uses a different diameter.

[the solitaire]

Even though there is still a considerable amount of manual pre-Ai lenses found on ebay and other online and offline sales points, I am not sure if a full scale production can be made profitable for what is essentially a niche product with dwindling numbers. Every Ai conversion ring sold is one down in the pool of lenses that might or might not be converted.

Added to that the collectors who prefer to keep their lenses mint and stock, the market share for such conversion rings will be too small (10-100 rings for each of th emore popular lens choices) that even creating a hype and a run on pre-Ai glass could not generate the revenue needed to pay off the machining cost or development cost.

I am afraid that this will always remain a DIY area as long as you do not find the Ai ring for the lens you wish to convert.

[Roland Vink]

So true.  A good / bad example is the factory Ai conversion rings produced for the 43-86mm f/3.5 zoom.  Nikon offered three such rings, and depending on the Serial Number of the lens being converted this determined what was the "correct" conversion ring. 

There is a bit more to it than that. There are basically two versions of the 43-86/3.5:
- the original one with the diamond rubber grip (including single and multicoated types). This one gets AI kits 68, 69 or 70.
- modern version with improved optics (includes K and AI versions). The K gets AI kits 65, 66 or 67

So both get three kits - as do all other zooms, the GN and ultra-wide lenses. This mystified me for a long time, but I think the reason is this:
Zooms and the GN run on cams which are less accurate than the focus helix found in primes. Ultra-wide lenses need to be built very precisely as even small variances can cause large shifts in focus. So when they were assembled, shims of varying thickness were added to ensure the lenses focused to infinity correctly. AI kits for these lenses were made in three different heights to match the varying shims, to ensure the AI tab engaged with the camera correctly.

In practice the link between the AI tab and camera doesn't need to be so accurate, almost any lens will accept any of the three AI kits, it is only in very rare cases that the AI ring is too short so does not engage, or too long and jams on the camera.

I really should add this to my AI modification page...