DIY lens dust removal.. good idea?

i recently bought a cheap nikkor 135mm f3.5 AI lens and it seems to be in pretty good condition except for some dust inside the lens. There isn't much though, and most of it is too small to be noteworthy.. however there is a large spec that i would like to get rid of.

I was planning to send it in and have it cleaned thoroughly, but after checking up on prices it just wont make sense to do it.

I'm thinking i could probably do this myself though, with some help. I've never taken apart a lens before, so im not sure how the mechanics look inside it. Anyone have a link to some schematics?
Will i be needing any special tools besides some small screwdrivers?
And finally.. Is this a good idea to do yourself?

It's probably not a good idea to try this yourself. It can be tricky to get the aperture linkages on a modern SLR lens back together. It is also good to use a repair shop that can recollimate the lens when they reassemble it.

Would i have to take the aperture linkage apart though? If i'm doing this myself i wouldn't attempt to take apart more then i needed to get to the dust. (everything seems to be pretty smooth, i just figured if i as sending it in i might as well get them to clean everything.)

What is the lens worth?

I've cleaned thousands of lenses - it is part of my day job - and lenses that I know and understand are a doddle as are large format or antique lenses, but one or two 35mm types I've not been familiar with I've screwed up big time. Problem is that sometimes to get access to the lens assemblies inside you have to dismantle the focussing and aperture assemblies.

One piece of advice is to use your digicam to photograph every step so that you can reassemble it correctly. Even better, video it. You may think it looks simple enough not to bother, but it is amazing how you don't realise that a part can fit 2 or 4 or eight different ways round until you try to fit it. Not that I've ever done this, of course ;-)

Biggest problem is if you disturb the focussing mechanism then you could lose the infinity focus setting and would have no easy way to set it up again.

It all comes down to cost - I'd say don't attempt it unless you won't be too upset if you scrap the lens.

Well.. the lens was cheap.. 40 $ us or so.. and seeing as having it cleaned professionally would cost twice that, i figured i'd give it a try. Worst thing that can happen is that i have to buy a replacement in better condition or send it off for cleaning and reassembly. Those alternatives would cost me about the same.
I've only shot one roll with it and i couldn't make out anything on the prints, but i hate the feeling of having it there, just lurking inside waiting to screw up a good picture
In short im pretty much set on atleast trying. The worst that can happen is that i have to pay what it would have cost to have it cleaned.

I'd like to know a bit more about what im doing before getting out the screwdrivers though. So i would still be very grateful if someone could point me in the direction of a repair manual/schematic etc. Any advice would also be appreciated.

EDIT: and thanks, steven_e007. That issue with the focusing was something i was unsure whether i could screw up or not and taking pictures along the way would definitely be a good idea. (just have to convince my sister to lend me the fujifilm s7000 i gave her cause i was convinced i wouldn't be using it anymore :/ I guess pro's aren't the only ones who use cameras as tools )

You'll probably need a spanner for the lockring, which will take care of much of what you might spend with a repair person. But what good is a project if you can't use it as an excuse to get another tool?
Try skgrimes, or micro-tools

I would do it myself (since I'm cheap ) only if the cost of cleaning it professionally cost more than the worth of the lens, but if the lens cost at 2 times or more than the cleaning fees, and only if the dust is costing me money and time in wasted photos, then I'll most definitely go the professional cleaning route.

I'm just a humble hobby photographer but I do know a little bit about cleaning optics from my day job, so I'll try to help with advice if I can....

First of all you are probably going to need a lens ring spanner wrench. A photo is attached (there are many designs). This will cost you a lot more than your lens, but maybe you can borrow one, source one cheap on eBay, or make one? You may decide to use the edge of a screwdriver in just one slot, or crossed screwdrivers. The ring will be very tight, so you will slip and then scratch the lens. Its kind of traditional!

Sometimes you can use a large rubber bung that just fits the ring. (You can actually buy sets of these in different sizes for huge sums of money, as some lens rings don't have slots for the wrench, but if you are lucky enough to get a rubber bung of just the right size, it will do).

The other problem is that cheap jeweller’s screwdrivers are often too thick for their blade width. Again, you can buy a pro set of drivers for 20 times the cost of your lens, or buy some very cheap ones and grind the blades down. Otherwise, you end up using a screwdriver that is far too narrow because that is the only way to find one thin enough. This will then slip and chew up the screw head.
(A bit more tradition! )

Anyway, the idea is to dismantle the lens as little as possible. Try not to take the optical assemblies apart if you can help it. If you get to the point of taking individual glass lenses out of their mountings then the lens may never be the same again as you will probably mess up the collimation.

I cleaned my Carl Zeiss 135mm lens last week and only had to take off the rear element to remove some dust. I had to take off the rear housing and disconnect the aperture linkage first, though. The effect of the lenses usually makes the dust appear a different size and in a different place to where you expect it to be, so go for the easiest bit to take apart first before you dismantle the front end!

Maybe you can post some pictures of the lens?

This is really going to sound like hacking.
I had heard that spanners are sometimes clamped in a vise to work on really tight lens rings. I found stainless steel stiffeners in an old windshield wiper blade that were .75mm thick and perfectly fit the notches in the lens ring of a lens I wanted to open up. I broke and de-burred the stiffener into two pieces and then clamped them tightly in a vise separated by the correct notch to notch distance. Lowering the lens upside down onto them to engage the notches, I was able to loosen the ring without mishap. (Even to my surprise.)
Once the ring was loosened, I turned the lens right side up and used the single screwdriver method described by steven_e007.

Risky... But ok if you are prepared to throw away the lens if you ruin it. It worked out fine for me, but thinking about doing it still gives my nerves a little tingle . Good luck, and don't throw out those old windshield wiper blades .

You've used the lens and the dust hasn't caused a problem. Stop worrying. It's not going to cause a problem. If it were, you'd already have seen it. I can't understand why you'd want to put an otherwise perfectly good lens to the wrench if there's no need.

Just remember--the plane of focus is going to be pretty far from the dust you're worried about.

bdial: Thanks for pointing me in the direction of those companies. The one skgrimes sells seems to be pretty sturdy and reasonably priced although i think it might need a little time on the grinder.. I might opt to just "be inspired" (aka steal some ideas :/) though, and build one myself.

film_guy: The cost of cleaning it would indeed be more than the worth of the lens.

steven_e007: Where to start, hehe. Professional advice is always appreciated and you've saved my ass a couple times already (and i haven't even started yet ). I'll post some pics of the lens and my progress as soon as i get hold of a spanner wrench and a digi cam. Still undecided if i'm going to make the wrench or buy it.

JJC: Heheh, this was DIY The distance from the rear of the lens to the ring is a little over 1cm though, so i think perhaps the windshield wiper parts would be a little too flimsy at that length. If i do make one myself i'll probably get a couple of those.. hmm.. i don't know what they're called in english.. what carpenters use to get nails into wooden panel without leaving a hammer mark. (looks a lot like what the skgrimes wrench tips are made of.) Either fix those into a vise or make some sort of bracket for them.

fschifano & Mr. Goldfarb: I'm aware that this isn't a serious issue and that i should probably let it be, but i'm a hopeless "tinkerer". I enjoy taking things apart to see how they work. Hopefully, i get away with it when it's time for reassembly .

Degenetron said:

Will i be needing any special tools besides some small screwdrivers?
And finally.. Is this a good idea to do yourself?

Click to expand...

I see nothing wrong with DIY, although my experience is only with relatively elderly Pentax/Takumar lenses. The main thing to me is (as Tomosy says in his books) take as much time as it needs and don't try to hurry. Don't be tempted to try to take short-cuts by using two screwdrivers in the opposing slots of retaining rings - take the time to make a tool for the job, which can be suitably profiled to avoid any convex glass surfaces etc.. Making such tools needn't take long, and once made, they are there for that time three years down the road when you need to take the lens apart for some other reason. On Pentax lenses that I've worked on, no glass removal has ever involved meddling with the focussing, but I can't speak for other manufacturers.
As someone else has said, don't take apart any more than you need to and if you can blow the crud away without having to wipe the surface of the glass, so much the better. (Lens cleaning and the marks it leaves has been raised elsewhere on APUG and is, for me, the biggest issue with lens disassembly).

Good luck Jim. This tape will self-destruct in five seconds (if you remember the original Mission Impossible!)

Steve