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11-22-2015, 02:38 PM - 1 Like   #1
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Building a Lens

Does anyone have any advice on building a lens? Sounds totally insane I Know. But I recently bought a giant lot of camera filters and bodies that were all mainly for repair. Off that the boxes had a couple lenses one of which being a Canon L 80-200mm f2.8 but the mechanics and body of the lens are totally destroyed leaving this perfect little pieces of glass inside the main setup. So on to my insanity. I am trying to figure out a way to design a lens for the Pentax K mount using the L series elements. Is it even possible, and for aperture I would most likely end up making a spot to slide in different rounded slides for sharper imaging. and focusing I was going to make push pull like a zoom except moving all the elements. Any clues or help would rock. And I have access to CAD and a 3-D printer the high school down the street has. They have let me use it in the past. Any tips and pointers would help. And the lens construction doesn't have to be perfect it just has to work on a pentax body. Thanks

11-22-2015, 02:54 PM - 1 Like   #2
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Nice ideas you got there - I am subscribing and will be looking forward to what others have to say
11-22-2015, 02:59 PM   #3
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It seems it could work. But the problem is building and designing a lens barrel for the elements thats accurate. I might have to make it piece by piece for the lens elements. Glues them as one. and then make a push pull focus setup on the inside using rails. the aperture should be fun too lol . Thanks
11-22-2015, 03:10 PM   #4
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What's not to like about a mad scheme? Keep us posted, Kmurphy! :-D

11-22-2015, 03:10 PM   #5
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I like your idea. Sounds like a fun experiment and you have good glass to work with. But there are some things to consider. For example, the registration distance for a Canon lens (EOS mount 44mm) is shorter than Pentax (K mount 45.46mm). You would have to be able to move the mount placement forward by 1.46 mm. Hopefully the rear element would allow that without protruding back into the camera body. Also, I don't know how many lens groups you will be playing with, but if more than one group has to move to focus, your push-pull idea might run into trouble (birds in flight would be interesting!) There is probably more that I can't think of. However, even if you converted it into a fixed 200/f2.8 that you could adapt to a Q7 or similar, you could be on a winner.,
11-22-2015, 05:19 PM   #6
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Makes sense. I am more thinking of making it for macro purposes because I really don't use telephotos often. But this is really just so i can learn how to properly make a lens. (Because I bought a lens grinder and polisher) . So I am hoping to figure out a way to make my own lens types. The push pull idea is kind of something I'm working on for my next lens project but that one will be disclosed later . I could adapt to my A5000 but that would take all the fun out of it. I was going to do three groups with 2 elements a piece. all in one main body. Connect a rail inside system so that technically the lens is two pieces. the main lens barrel and then the focus outer barrel. The rails would have locking spots for fixed focus on something acting like a zoom focus prime (name work in progress). I think I might be able to get it to work but it should be interesting. Any help or info on this stuff would be awesome to have. Pm me anything so I can work it into my design.
11-22-2015, 05:43 PM   #7
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Your project is a lot more complicated than what I did.
Look at this tutorial I made, very simple though:
Homemade Camera Lens
For aperture I could suggest a 'Petzval' aperture system:

These push into a slot in the lens

Last edited by bertwert; 11-22-2015 at 06:00 PM.
11-22-2015, 05:45 PM   #8
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The closest I got to making lenses from scratch (glass slugs to be polished into convex or concave surfaces) was years ago with an astronomy club. They may be an excellent source for lens construction. My only suggestion is to initially consider very simple lens designs from the 19th and early 20th century. Even today, Lensbaby Velvet, for example, uses 4 elements in 3 groups, and many inexpensive enlarging lenses like the $100 Beslar or Rodenstock triplets (3/3) work amazingly well.

I once made a pinhole that worked really well attached to a 35mm FSLR, but could not get it to work well on a DSLR. Never figured out if the circles of confusion were too large or if it had to do with the direction of the light striking the film/sensor plane at various angles. Film is more forgiving than a CMOS sensor.

11-22-2015, 06:13 PM   #9
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QuoteOriginally posted by bertwert Quote
Your project is a lot more complicated than what I did.
Look at this tutorial I made, very simple though:
Homemade Camera Lens
For aperture I could suggest a 'Petzval' aperture system:

These push into a slot in the lens
Thats along the lines what I was thinking. Since I am gutting all the elements out of the lens and working from the mount forward. Its should be interesting. I just started my rough drawing of the lens. The push pull focus system is definitely going to be tough to figure out. But I think since it will be a prime that I am going to mainly use for macro, It should be interesting. For focusing I am wondering if I have to move all the elements forward and back or only the ones closest to the sensor. That part I find a bit confusing. I am hoping that i could just move the rear elements because it would make my push pull system much easier but I am going to assume that I will have to move all elements.

---------- Post added 11-22-15 at 06:14 PM ----------

QuoteOriginally posted by Alex645 Quote
The closest I got to making lenses from scratch (glass slugs to be polished into convex or concave surfaces) was years ago with an astronomy club. They may be an excellent source for lens construction. My only suggestion is to initially consider very simple lens designs from the 19th and early 20th century. Even today, Lensbaby Velvet, for example, uses 4 elements in 3 groups, and many inexpensive enlarging lenses like the $100 Beslar or Rodenstock triplets (3/3) work amazingly well.

I once made a pinhole that worked really well attached to a 35mm FSLR, but could not get it to work well on a DSLR. Never figured out if the circles of confusion were too large or if it had to do with the direction of the light striking the film/sensor plane at various angles. Film is more forgiving than a CMOS sensor.
Do you know where one could find the old lens designs and measurements of those lenses? That would help immensely in my design. And since this will act like an M42 lens with no aperture lever it should be much easier to mess with.
11-22-2015, 06:16 PM   #10
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I don't know if you see my focus system, but as I said, your project is levels above mine
11-22-2015, 06:27 PM   #11
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If you have the measuring tools, I think the easiest is to simply deconstruct some "as is" lenses from keh or look in craigslist for lenses retired from mold/fungus. At my school, I run a darkroom with 21 enlargers and despite my best effort, we replace enlarging lenses every 5-10 years because of hazing. You may inquire at a local high school or college that either has a box of discards or has recently closed down their labs.

Here's a few links that at least gives you some designs and lens names:
http://www.abload.de/img/triplets_v1jajb.png
List of lens diagrams: triplets, planars & hybrid lenses
11-22-2015, 06:29 PM   #12
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Oh yeah It's like the idea I have. The push pull system. Moving the tube back and forth. So you found the milimeter measurement by seeing what comes into focus. That part is also where I need help. Like locating infinity and closest focus. I believe the lens will end up being f2.8 at its fastest and I'm shooting for somewhere in between 80-200mm for focal length but the tube part is gonna be hard. I have it figured out now that I'm going to measure each lens element and make a thing casing for each that extends down a little and allows for superglue to stick each grouping together. How does one do the whole focal length tube distance thing? In more depth than your description on instructables. I'm just doing my rough drawings now to figure out how big this monster will be

---------- Post added 11-22-15 at 06:56 PM ----------

QuoteOriginally posted by Alex645 Quote
If you have the measuring tools, I think the easiest is to simply deconstruct some "as is" lenses from keh or look in craigslist for lenses retired from mold/fungus. At my school, I run a darkroom with 21 enlargers and despite my best effort, we replace enlarging lenses every 5-10 years because of hazing. You may inquire at a local high school or college that either has a box of discards or has recently closed down their labs.

Here's a few links that at least gives you some designs and lens names:
http://www.abload.de/img/triplets_v1jajb.png
List of lens diagrams: triplets, planars & hybrid lenses
I have some enlarging lenses laying around specifically a Wollensack that has like a 20 blade aperture. I might slap a pentax mount on it and see what happens. I could make a focusing mech for it but I dont want to measure the infinity and close focus just yet. I more want to put the lens groupings and elements up for the Pentax L ...MM. I think that is what I will call the lens when finished. Do it up in a nice black and on the side have the focus scale and have the Name written in nice white lettering. But now I'm getting ahead of myself. This project is going to be a while. and when I figure it out. I can hopefully try to make another one from some old Minolta glass!
11-22-2015, 07:40 PM   #13
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QuoteOriginally posted by kmurphy220 Quote
Oh yeah It's like the idea I have. The push pull system. Moving the tube back and forth. So you found the milimeter measurement by seeing what comes into focus. That part is also where I need help. Like locating infinity and closest focus. I believe the lens will end up being f2.8 at its fastest and I'm shooting for somewhere in between 80-200mm for focal length but the tube part is gonna be hard. I have it figured out now that I'm going to measure each lens element and make a thing casing for each that extends down a little and allows for superglue to stick each grouping together. How does one do the whole focal length tube distance thing? In more depth than your description on instructables. I'm just doing my rough drawings now to figure out how big this monster will be

---------- Post added 11-22-15 at 06:56 PM ----------



I have some enlarging lenses laying around specifically a Wollensack that has like a 20 blade aperture. I might slap a pentax mount on it and see what happens. I could make a focusing mech for it but I dont want to measure the infinity and close focus just yet. I more want to put the lens groupings and elements up for the Pentax L ...MM. I think that is what I will call the lens when finished. Do it up in a nice black and on the side have the focus scale and have the Name written in nice white lettering. But now I'm getting ahead of myself. This project is going to be a while. and when I figure it out. I can hopefully try to make another one from some old Minolta glass!
Best of luck, but remember the destination is usually not nearly as rewarding as the journey.
11-22-2015, 08:11 PM   #14
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The journey is always fun! My last adventure like this was taking apart my M50mm f1.7 and putting it back together. Fun maybe but I learned alot. Not a hard lens to screw around with either. I think this might be a pretty big lens considering how many elements it will be. The lens should be pretty hefty after it all. I'm thinking the barrel needs to be pretty thick for support and It's going to use a metal mount as well from an old 28 prime I had in pieces.
11-22-2015, 08:30 PM   #15
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Here is some.....inspiration?
The Reclusive Peeping Tom Photographer and his Cardboard Camera | Messy Nessy Chic
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