i'm trying to build a lens

[notelliot]

everyone is probably going to think i'm retarded, or that this isn't possible. but, i want to try this anyway.
i have a nikkor 28-100/3.5-5.6 G that has a broken mounting ring. first off, i want to switch out the plastic ring for a metal ring which will be really hard, but theoretically possible. i might not get the metering to work, or the AF, but that's fine. the other thing i'm going to try is opening up the aperture to F1 (haha, yeah - a 28-100/1). i'm expecting this thing to turn out either really soft and full of CA and some distortion at wider focal lengths, or really sharp and full of CA and some distortion. this lens doesn't need to work like an L series, or one of nikon's higher-end zooms, i just want to see if i can do it.

what i'm having trouble with is getting the mounting ring off. the screws will not turn. i'm assuming they're glued. and i'm wondering, of course, if anyone has any experience with either experimental or certified lens repair and could shoot me some pointers. thanks in advance.

 

[Iron Flatline]

You know... to make an f/1 you're going to have to seriously widen the camera - the f-stop is a proportional measurement. That means if your lens is 60mm long (not in the focal length sense, but actual length) the aperture would have to open 60mm across.

 

[PhotoSlip]

I haven't disassembled a nikkor lens before, but I have removed the mounting ring on a Sigma and Canon lens. Both were broken already and not worth fixing.

The Sigma mounting screws were quite easy to remove. The Canons were very difficult. I had to use the smallest screwdriver I had and couldn't hold the screwdriver hard enough to turn the screws. I took a small pair of pliers to rotate the screwdriver while pushing down on the screwdriver really hard so as to not strip the screw. All the screws came out. I reassembled with no problems to the threads in the lens. I say no problems, but I have never used the lens extensively after reassembling as I didn't fix the lens. Just got a good look at what's going on inside. There are a few screws (usually the larger ones) that are this tight. Make sure you put them back on this tight as they'll strip if there is some wiggle room for them to play with. Also make sure you don't strip them during tightening....big dilemma getting the right tension...


As you're not going to try to keep the electronics, there's no need to becareful not to break any of the ribbons. A lot of the internals are plastic and are brittle. On the Sigma, the ribbon was broken and not worth replacing. I removed the ribbon and used really soft wires and fixed the problem. Only problem was, I dropped the focus lens. Not far, about 8" off the table. A leg on the mount broke off instantly. I epoxied the leg back on, but I still have serious focus issues. I'm not sure if it's the mount or I assembled it wrong, but that's not the point...the plastic is real hard and real brittle. Don't drop anything. Oh yeah, and the screws are all similar in size but they're not the same, so don't mix them up. Place them back in the holes they were in during disassembly so you don't have to remember where they're supposed to go....

Clean all the lenses before reassembly and during reassembly. Just keep cleaning them. I reassembled once and found a big finger print all over the interior lens. Had to disassemble all the way to clean it off.



That's all the advise I can give you as an experimenter.

 

[jstuedle]

Nikon lens mounts do not use standard philips head screws. They are cross point screws, you can find the drivers at Micro-tools: http://www.micro-tools.com/store/home.aspx
They usually are really tight, so use caution to not strip out the driver slots.

 

[GreenSlime89]

So I could try that with an old, cheap lens at work? I work at an opticians where I have access to an optical screwdriver set, I'll see if I can do it once I get my 70-200mm F/2.8 L USM. (I'll buy another lens to do this on but that's what I've got to get before I waste any more money) Should I try to use some lenses from work to increase the focal length? I have a wide range of lenses with a 65 diameter. (-6.00 - + 9.00) Would that be any use? All I have to do is pay for each lens I use (about £5) so would that be worth trying?

Ah, what If I tried to build one from scratch, own lenses from work, aperture blades and ring from an old lens, mount from another EOS lens and a barrel from somewhere...? It'd be something if it worked - a 100mm F/1?