Stripdown – Project #2

Two lenses arrived in the post last week: identical 135mm f3.5 Super-Takumar primes built in the very early 1970s.Both were sold together, as faulty: ‘with dust/fungus in the lens’. In the past few days a few other things have turned up in the post or have otherwise been ‘acquired’ (a dropper pipette I stole from the lab – the perfect reward for a wasted four months of my life). I now have on the desk in front of me the following:

  •  Two ‘mechnically fine’ lenses with associated internal ecosystems
  • One 100ml bottle of isopropyl alcohol
  • One dropper pipette (stolen)
  • Six precision screwdrivers in various sizes
  • One roll of kitchen towel
  • One set of instructions (no pictures or diagrams!) purloined from the internet

Thusly armed and sporting a fetching can-do attitude, I set about stripping and cleaning my first ever lens. During the space of the next few hours, a few things were added to my toolbox – namely a homemade wrench (made of broken USB housing), a Stanley knife, a large sewing needle and a hacksaw (what can I say? Precision tools for a precision job!).

The start was made somewhat easier by the fact that the lens top ring, when I opened the case, just fell off. Ominous sign, I thought – perhaps these lenses were slightly more broken than the eBay advert had suggested. Within about ten minutes I had the focusing ring off, unscrewed the helicoid that lets the lens extend when you focus it, and had lined up a lot of general bits and bobs on my worksurface. It was neatly arranged. I was pleased. I had both the front and rear element groups out and all that remained now was to separate them and clean them, and reassemble the lens to create a functional whole! The rear lens group was a single element so I didn’t even need to remove it from its mount – I just droppered some alcohol on it and wiped it down with lens tissues. Done. I turned my attention to the front element group – three pieces of optical glass in a metal cylinder, held down by retaining rings. Piece of piss.

Fighting for an hour to get the first retaining ring off was not a lot of fun. I made tools, carved grooves (you were wondering when the hacksaw would make an entrance? This is that time), tried to dissolve the sealant varnish with 99% alcohol, all to no avail. In fact, it was only when I destroyed a USB stick housing to create a wrench that would fit the hacksaw grooves that I eventually made progress and lo! the ring gave. Such satisfaction, as the front element popped out into my hand. I was victorious.

A quick glance revealed a second retaining ring for the second element. Crap.

To cut a long struggle short, I managed to get everything out and set about cleaning up the glass. As it turns out, putting the elements back in without leaving any fingerprints on them wasn’t as easy as you’d think – those low engineering tolerances mean that everything fits pretty tightly so it wasn’t possible to just drop them back in – I had to make sure they were perfectly aligned with the barrel of the lens group when I replaced them. Cue the sewing needle for pushing the lens element down evenly (using the blunt end, of course).

Reassembly was initially painless – I managed to set the focus correctly using my camera, and fitted the aperture ring and depth of field scale in places where they belonged, and that they were accurate. It was about the time I was putting the focusing ring back on that I realised something terrible – three bits of metal that hold the name plate on the lens were blocking access to the screw holes below to secure the ring, and I had to disassemble the lens again and put it together at a different angle. Damn.

This is the lens now.

As you can see, the top doesn’t look finished, and it isn’t. Nor am I capable of making it so. This is not because I stuffed up the construction and have forever ruined the lens. In fact, it works just fine. You remember up near the top of this post, where I said the top ring just ‘fell off’ when I opened the case?

Someone has clearly tried to fix this lens before, and they broke the end plate in doing so. You can’t unscrew the name ring anymore, and as such you can never re-attach it as it has become impossible to screw down. The lens works, but it is vulnerable to dust and dirt clogging up the focusing mechanism. Frustrating. I have spoken to some engineering friends who might be able to re-thread the broken section and make it usable, but untl then I am left with only one option – sacrifice another 135mm f3.5 Takumar and replace the top from that. I do have two of these, it is true, but the second one is in much better condition so to kill it for this would be criminal.

For now, this lens will live in my desk. It has been an interesting exercise (and I will be able to strip, clean and sell the second, better-quality lens much more efficiently because of it) but still. Bit frustrating to be pipped at the post by something that wasn’t even my fault! Such is life, I guess. Lessons learnt from this one went into the other, better-condition lens though, and one out of two ain’t bad. Ended up with a £50-60 lens for £24 (with, of course, a random spare lens that I also now own) and the project has paid for itself.

VERDICT: SUCCESS

(I will put a complete how-to somewhere else so that anyone who wants to clean out one of these lenses can do so without too much grief, but I won’t bore y’all with the whole step-by-step account)

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