Despite the encouraging tone of your fourth grade teacher, trust me, having an active imagination is a curse. As an adult it’s far worse, since you have more control over your own actions and more time to develop bad ideas. In spite of the countless other examples I could bring up, I will confine my comments to one particular result of my over-active brain, a little lens hacking project that I recently undertook.
This started with my acquisition some time ago of an Industar I-50 50/3.5 collapsible LTM lens. It came along with another lens (my FED 50) at no cost. The reasons for this lens being essentially free are simple: one, it had a front element that looked like it had gone ten rounds with a belt sander, and two, it had had its chrome stripped, fake Leitz Elmar markings added, and was a gaudy highly polished brass mess. It probably came from one of those ridiculous ebay fake Leicas that they seem to churn out in Russia these days.
I kept it thinking that one day I would either try to polish up the front element or do something with the mount. The first didn’t happen because I have plenty of other non-abraded, non-pimped-out LTM 50s that work just fine. As the misery of this past winter became more severe, my mind started to think about what I could jam into the mount and actually make work. I’m not sure in what order the various points of inspiration came, but the two main contributors were the Leitz Elmar 35/3.5 and the Nikon L35AF.
The former is a super compact lens that looks perfect on a Barnack Leica. Having recently found myself in possession of such a camera, and not wanting to shell out big money for the scarce wide Elmar, I started to think about building a 35mm lens out of the old I-50. I figured that any number of cheap point-and-shoot cameras could be used to supply the optics, which I would then adapt to the Industar, retaining the aperture setup, the focusing helicoid, and the mount.
But what old compact should go under the knife to give up its precious lens for this project? My requirements were simple: good and cheap. Something produced in large numbers, with a reasonably high quality lens, that would hopefully be easy to take apart and modify. I started investigating the options and fairly soon stumbled across an article about the lens on the Nikon L35AF. Now, you know perfectly well that the internet is full of articles about lenses, many written by people whose sole qualification for providing in-depth technical analysis is that they bought the lens last week and are trying to justify their purchase.
But this article was different – it was written by Nikon engineers and published on Nikon’s own site. What it described was a rather unique 35mm lens: a modified Sonnar formula rather than the more usual Tessar, well-corrected, with high resolution and fairly modern contrast levels. Nikon made a considerable effort to raise the bar for optical quality in compact consumer cameras and appears to have succeeded, judging by the high regard in which the L35AF – also known as “Pikaichi,” or “top notch” in Japanese – is still held.
A quick ebay search turned up plenty of examples. I selected a cheap one that looked used but not abused and apparently didn’t work. No reason to hack up a working camera when a broken one will do just fine. I had it in hand in a week and began stripping it down. This turned out to be quite easy, and very soon the lens assembly was out. I already had the I-50 taken apart, so the process of engineering the mating of the two into an unnatural creation of my own design began.
The optics of the Nikon are entirely contained in a small plastic housing with the helicoid cast into the outer surface and a wide collar with holes to engage the autofocus actuating mechanism. This was very handy, as it meant that I didn’t have to mess around with multiple pieces, and especially with keeping them properly aligned and spaced. The collar was far too wide, but I didn’t need it, so out came the Dremel and off it came. The remaining portion was of a somewhat smaller diameter than the space in the I-50 barrel, so the gap would need filling somehow.
The major engineering challenge was always going to be getting the optical block the right distance from the film plane to achieve infinity focus. In order to make the Industar body work, the barrel was going to have to be cut off and fixed in the collapsed position; this mimicked the look of the Elmar 35 almost exactly. Doing this proved insufficient; even placed as close to the aperture as possible, the glass was too far away, making infinity focus impossible. I had to grind down both the top surface of the mount and the edge of the front plate to get them lower in the body. Fine-tuning would be done later as needed with shims.
Once I got the barrel positioned deep enough, I had to find a way to secure it to the mount, as well as to secure the optical block to the barrel. Related to this was the need to keep the optics as close to perfectly centered as possible. I decided to try something non-destructive first, which turned out to be a fairly good solution: O-rings. A series of different sized rings hold the barrel quite securely in the mount, restricting movement yet easily removed (this is important when hacking together a lens, as you will be assembling and disassembling a lot). The optical block was trickier, as the O-ring had to be snug enough to hold the glass firmly in place, yet also allow it to reach full depth, and at the same time not restrict the turning of the aperture ring. Eventually, after much experimentation, I figured out the right size for this as well.
I was a bit concerned about indexing the aperture, but through a remarkable bit of good luck, the measured apertures calculated out to be close enough to correct (within a few tenths of a millimeter) to simply use the index marks on the lens face (in the Continental scale, 3.5 to 18) to correspond to the modern system from 2.8 to 16. The aperture is directly behind the glass, which is exactly the same setup as the L35AF. It’s also a nice round aperture, unlike the trapezoidal two-blade arrangement on the Nikon.
Countless hours of fiddling and fine-tuning were required to get things right (or at least good enough), especially infinity focus. There is really no margin for error with this – it’s either right or it isn’t. My Fuji X-E1 with LTM adapter proved indispensable in this; without a digital camera to check the focus, I would have been using a ground glass, which would have been far more time-consuming and in all likelihood less precise, given the small size of a 35mm film gate.
There are still a few issues. Foremost among these is that the rangefinder coupling of the Industar lens is completely wrong for the wider Nikon optics. I knew this going in, and resolved that this was going to be a scale-focus project from the get-go. As long as infinity was at the right place, everything else could be determined and marked. For starters I established focal points for 1, 2, and 3 meters and marked those. More precision would be nice, but it really isn’t necessary – most of my use will be zone-focused for street photography, set at 3m and moderate aperture.
The beauty of the the thing is its size. It’s just tiny, barely bigger than a body cap. The ergonomics are dated, but that’s true of most of my lenses. The glass is recessed well into the barrel, so there’s really no need for a lens hood. True, you need an external viewfinder with most cameras, but even so the whole thing fits easily into a pocket.
I’m not sure I’m entirely happy with the black finish I applied (I wasn’t leaving it polished brass); I may strip it down and try a different color. I also have an idea about adding click stops for the most-used focus settings, at least for 3m. If I can work that out it would be the perfect time to refinish.