Easy-to-disassemble lens

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Alphoid Veteran Member • Posts: 5,647
Easy-to-disassemble lens

What's a cheap, easiest-to-disassemble (and reassemble) lens?

Teaching kids.

It doesn't need to reassemble optically calibrated, but it should work (we use u4/3, since anything adapts).

Wide-ish aperture preferred. A big part of this is understanding what the aperture does, and that's easier if you can have big bokeh balls.

I'm thinking some historical lens from a now-dead MF mount? Or a cheap Chinese CCTV lens of some kind?

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Klaus dk
Klaus dk Veteran Member • Posts: 6,946
Re: Easy-to-disassemble lens

I have an old enlargement lens with a manual aperture. When you turn the ring, the aperture opens or closes. No need to pick it apart.

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Gerry Winterbourne Forum Pro • Posts: 17,866
Re: Easy-to-disassemble lens

Alphoid wrote:

What's a cheap, easiest-to-disassemble (and reassemble) lens?

As Klaus says, you don't need to take a lens apart to show what you describe below.

Teaching kids.

Last year I explained these things to my 10-year old granddaughter. (I also explained focal length by using two bare lenses - 50mm and 100mm - like a magnifying glass to focus a ceiling light on paper on the floor, and measuring their distances above the floor).

You just need to hold the lens in front of the face and move its aperture lever. You can even show that the size looks different front and back, and that it's the front size that's used for f-number.

It doesn't need to reassemble optically calibrated, but it should work (we use u4/3, since anything adapts).

Wide-ish aperture preferred. A big part of this is understanding what the aperture does, and that's easier if you can have big bokeh balls.

I'm thinking some historical lens from a now-dead MF mount? Or a cheap Chinese CCTV lens of some kind?

If you really want to take it apart, buy the cheapest you can find and some tiny screwdrivers.

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OP Alphoid Veteran Member • Posts: 5,647
A bit more advanced

I think they kids get focal length and (roughly) aperture.

I'd like to do some things which are a little bit more advanced: for example, it'd be nice to put in an aperture with a different shape (cut out of a piece of paper), and see bokeh balls. Or one with two holes side-by-side. And then talk about PSF and code up something along those lines. Or that sort of thing.

If you really want to take it apart, buy the cheapest you can find and some tiny screwdrivers.

A lot of lenses require specialized tools, or have tons of parts which are really hard to reassemble.

  • I have a few CCTV lenses at home, which I have no chance of opening. I think they might be glued together? I'm not really sure, but there are no exposed things I can turn.
  • Minolta lenses I've opened for cleaning required spanner wrenches and things like that. In all cases, it was a super-involved process with fine parts (it doesn't help that they have AF, electronics, and all sorts of fanciness we don't really need for this).

One of the points is you want to do these sorts of things quickly, so it's not a one-hour operation each time you want to tinker with something.

armin304 Contributing Member • Posts: 667
Re: A bit more advanced

Alphoid wrote:

I think they kids get focal length and (roughly) aperture.

I'd like to do some things which are a little bit more advanced: for example, it'd be nice to put in an aperture with a different shape (cut out of a piece of paper), and see bokeh balls. Or one with two holes side-by-side. And then talk about PSF and code up something along those lines. Or that sort of thing.

If you really want to take it apart, buy the cheapest you can find and some tiny screwdrivers.

A lot of lenses require specialized tools, or have tons of parts which are really hard to reassemble.

  • I have a few CCTV lenses at home, which I have no chance of opening. I think they might be glued together? I'm not really sure, but there are no exposed things I can turn.
  • Minolta lenses I've opened for cleaning required spanner wrenches and things like that. In all cases, it was a super-involved process with fine parts (it doesn't help that they have AF, electronics, and all sorts of fanciness we don't really need for this).

One of the points is you want to do these sorts of things quickly, so it's not a one-hour operation each time you want to tinker with something.

Try to get a cheap medium format lens. At least the lenses for my Kiev 88, made in USSR, were easy to dismantle and reassembled again. I should know, the apertures of all of them were stuck at some time, because the grease used by the factory for the helicoid was really bad and got fluid like oil and got onto the aperture. No special tools needed, but a special lens wrench would have made it easier.

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Leonard Migliore
Leonard Migliore Forum Pro • Posts: 18,237
Go large format

Alphoid wrote:

I think they kids get focal length and (roughly) aperture.

I'd like to do some things which are a little bit more advanced: for example, it'd be nice to put in an aperture with a different shape (cut out of a piece of paper), and see bokeh balls. Or one with two holes side-by-side. And then talk about PSF and code up something along those lines. Or that sort of thing.

Then you want something like an old Speed Graphic lens:

https://www.keh.com/shop/135-f4-7-optar-graphex-bt-bipost-4x5-35-mt-lens-685075.html

You remove the front and rear groups from the shutter by unscrewing them. Quick and easy. And for some variety the lens will focus with just the front group.

Any large-format lens in a Compur shutter will do fine.

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Leonard Migliore

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OP Alphoid Veteran Member • Posts: 5,647
Re: Go large format

That seems ideal!

Large format would also allow us to play with tilt, shift, and similar adjustments too.

I'm a little concerned about f/4.7, though. Used with an u4/3 format, that gives basically infinite depth-of-field in many cases. Do you know if something like this might work well?

https://www.keh.com/shop/bronica-75mm-f-2-8-nikkor-p-lens-for-ec-s2-system-67.html

Leonard Migliore
Leonard Migliore Forum Pro • Posts: 18,237
Re: Go large format

Alphoid wrote:

That seems ideal!

Large format would also allow us to play with tilt, shift, and similar adjustments too.

That's only if you get a view camera along with the lens. That would be a lot of fun but bumps up the cost quite a bit, especially if you want to actually take pictures.

I'm a little concerned about f/4.7, though. Used with an u4/3 format, that gives basically infinite depth-of-field in many cases.

Large format lenses have long focal lengths. The one I linked to was 135mm, and that's on the short side for 4X5. I can assure you that you will not suffer from excess depth of field.

I didn't catch the part about using the lens with µ4/3. I don't think you'll find a standard adapter for large format lenses to a µ4/3 camera since they all go on lens boards. So that will be a problem.

Do you know if something like this might work well?

https://www.keh.com/shop/bronica-75mm-f-2-8-nikkor-p-lens-for-ec-s2-system-67.html

I doubt if it's easy to take apart. It's probably the same as a 35mm SLR lens.

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Leonard Migliore

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OP Alphoid Veteran Member • Posts: 5,647
Re: Go large format

Leonard Migliore wrote:

Alphoid wrote:

That seems ideal!

Large format would also allow us to play with tilt, shift, and similar adjustments too.

That's only if you get a view camera along with the lens. That would be a lot of fun but bumps up the cost quite a bit, especially if you want to actually take pictures.

Well, I'm not sure that will be a problem. I can physically move the lens (or perhaps more easily, the camera), and put a dark cover around the whole thing. I don't think it will be too tough to rig something up.

I need to take pictures, but I'm fine taking pictures of just one thing on a lab bench.

I'm a little concerned about f/4.7, though. Used with an u4/3 format, that gives basically infinite depth-of-field in many cases.

Large format lenses have long focal lengths. The one I linked to was 135mm, and that's on the short side for 4X5. I can assure you that you will not suffer from excess depth of field.

Good point. I missed that. Thank you.

I didn't catch the part about using the lens with µ4/3. I don't think you'll find a standard adapter for large format lenses to a µ4/3 camera since they all go on lens boards. So that will be a problem.

I'm sure I can rig something up. An adapter needs to be portable. Here, I can:

  • Stick a camera on a pole mounted to the workbench (or a tripod, if flange distance allows)
  • Cut a hole in a box, and mount the lens inside the hole
  • Focus the lens to infinity, and move the box until infinity is in focus
  • Tape down some kind of stop so I can get the whole thing in the right place again

Or something along those lines.

Gato Amarillo Veteran Member • Posts: 7,017
Re: Go large format

This could be a plan. On most of the old large format lenses it's easy to remove the front and rear cells to see the diaphragm -- or drop in an alternate aperture. If you really want to get to the internal parts it's not too hard but you have to get into the shutter mechanism, which is quite a few very small pieces.

OP Alphoid Veteran Member • Posts: 5,647
Re: Go large format

I also don't really need a working shutter. So if I break it, no biggie.

A u4/3 camera will have a built-in shutter for photos (although I expect most of the time to just be streaming video, so we can see what the camera is seeing).

I ordered one. We'll see how it goes!

NickZ2016 Senior Member • Posts: 1,190
Re: Go large format
1

No idea about 4/3 but there are Graflok backs to mount F mount (I assume others exist) cameras. Find an old monorail with a Graflok back. Bellows don't need to be perfect. Small leaks can be taped. Indoors unlikely to be a huge issue. Even if it doesn't lock down perfectly would it matter?

Kids can look at the ground glass. Much more wondrous than any viewfinder. Even a tiny little 4x5. Of course if you could find an 8x10 even better.

Mount the back and digital camera if you want to take photos.

DOF is a function of focal length,F/Stop and sensor size . Or really CoC.

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DavidP03 Regular Member • Posts: 424
Re: Easy-to-disassemble lens

Alphoid wrote:

What's a cheap, easiest-to-disassemble (and reassemble) lens?

Teaching kids.

It doesn't need to reassemble optically calibrated, but it should work (we use u4/3, since anything adapts).

Wide-ish aperture preferred. A big part of this is understanding what the aperture does, and that's easier if you can have big bokeh balls.

I'm thinking some historical lens from a now-dead MF mount? Or a cheap Chinese CCTV lens of some kind?

A Russian Helios 44, cheap, plentiful and easy to pull apart. 
A side note, if you reverse the front element the swirl effect increases substantially

Kind regards, David.

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OP Alphoid Veteran Member • Posts: 5,647
Good call!

Color me impressed. I can point the lens at a window, put a piece of white paper behind it, and I get an image of the great outdoors. No box. No nothing. This is awesome with kids.

Wow!

An 8x10 would have been even better, but probably not worth the 4x-10x price difference.

I turn a knob to set shutter speed. I slide a slider to set aperture. There's a thing which seems to wind up a spring (needed for the whole thing to work), and a lever which opens (and on bulb mode, then closes) the shutter. Then there are a pair of things at the bottom, which look a bit like electrical connectors or knobs or something. I'm not sure what those do.

And I need to figure out assembly, disassembly, and if there are any calibration issues. I can't turn it by hand to unscrew.

Do you know if there's somewhere I can read about these? I don't want to apply force unless I know I'm not breaking something.

Gato Amarillo Veteran Member • Posts: 7,017
Re: Good call!

Can you tell us what you got? Or better post a photo or link to a photo?

Probably one of us can help you if we know just what it is.

Thanks.

And the electrical connectors are flash sync -- possibly a pair of round posts. If you see a switch marked M and X, M is for flash bulbs, X for electronic flash.

Gato

OP Alphoid Veteran Member • Posts: 5,647
Pictures of lens

The exact one Leonard Migliore recommended (I'm old enough that I've learned to listen to my betters):

The rear group is very obviously screwed in. It would require a spanner wrench to unscrew. I'm not sure if there's any lock screw or anything else holding it in. I'm also not sure if I take it out, whether I screw it in all the way, or tighten to a specific distance, and if so, how precise that ought to be.

Leonard Migliore
Leonard Migliore Forum Pro • Posts: 18,237
I had one of those

Alphoid wrote:

The exact one Leonard Migliore recommended (I'm old enough that I've learned to listen to my betters):

The rear group is very obviously screwed in. It would require a spanner wrench to unscrew. I'm not sure if there's any lock screw or anything else holding it in. I'm also not sure if I take it out, whether I screw it in all the way, or tighten to a specific distance, and if so, how precise that ought to be.

That looks like what was on my Speed Graphic. I don't recall there being any setscrews holding in the lens groups but those things have been in there around 70 years so I doubt if they'll unscrew easily.

I wouldn't worry about how far to screw them back in. You're not concerned about achieving optimum optical quality, which wasn't that good anyway.

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OP Alphoid Veteran Member • Posts: 5,647
Re: I had one of those

Thank you.

So, to clarify:

  • Twist rear group (where I see the threads) as hard as I can with spanner wrench. Mark where it was, but don't worry about calibration.
  • Twist off front group (part which sticks up in front) with whatever wrench will grab it. It just turns and comes off. Twist as hard as I can. 
  • You focus by moving the lens. There is no focus adjustment otherwise. 
  • Two knobs sticking out are for flash. 

Is that all correct?

Gato Amarillo Veteran Member • Posts: 7,017
Re: Pictures of lens
1

Alphoid wrote:

The exact one Leonard Migliore recommended (I'm old enough that I've learned to listen to my betters):

You should be able to grip the silver ring around the part that says Optar and the serial number and unscrew the front optics assembly all in one set. It should come out by hand, but something like a rubber jar lid gripper may help

On the rear, the outer part with spanner notches is the retainer ring to hold the lens in the board. It should unscrew easily. The part it threads onto is the rear lens barrel -- it should unscrew from the shutter like the front.

Removing those pieces will reveal the shutter and diaphragm blades.

The shutter timing mechanism is under the plate with Graphex and the f numbers. Usually there are a couple of screws to remove this, but I don't see them here. Possibly it is held in place by the front lens barrel and will lift off after you unscrew that.

OP Alphoid Veteran Member • Posts: 5,647
Re: Pictures of lens

Jar gripper and a good hard twisted unscrewed the front group. I'm always scared to use force like that until I know I'm twisting the right thing.

As promised, the aperture is right there. It now twists freely, and I don't think there's any reason to remove the rear group. I think I'm all set.

Thank you all so much!

Now, I just need to rig it up to an old u4/3 camera.

This is fun!

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