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06-03-2012, 08:37 PM   #1
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homebrew lenses

I'll be offline for a little while starting tomorrow morning, hopefully will be back in a few days. While I'm gone, here's some stuff for you glass fiends to chew on. Maybe it's old news for some, but I just found the Flickr Homemade Lens discussion group. Some fascinating stickys:

* Flickr: Discussing DIY camera lens tutorial in Homemade Lens
* Flickr: Discussing DIY Tilt-Shift Tutorial by Bhautik Joshi in Homemade Lens
* Flickr: Discussing DIY Soft Focus Lens: Replicating the Rodenstock Imagon in Homemade Lens

Whatever free time you thought you had will rapidly disappear. Have fun!

06-03-2012, 09:19 PM   #2
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a year back, someone demonstrated many of her homemade lenses in a local forum, here is her presentation,

DIY: Making your own lenses by Meghana Kulkarni
06-04-2012, 06:05 AM   #3
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The mere suggestion that I undertake such a thing qualifies as cruel and unusual punishment.
06-04-2012, 07:17 AM   #4
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OK Rio, I am chewing on a PK single element 1:1.8 77mm portrait lens (with a waterhouse of course).

That project will be after I work out how to machine the bastard (not swearing, ..really) 39 mm 1"/26 Whitworth thread for mounting the Roganon into my PK mount slide copier.

In the history I read, Leica had British lathes which caused this crazy lens mount. Not that it matters for lenses, but the American inch is different to the British inch, and those Canadians later caused another inch which is different again....
What does matter for me is that I need a 55 degree whitworth tool for my lathe to cut the thread, as American threads are 60 degree.
Furthermore, when I look at the Roganon M39 thread through a Loupe, it is not an original Whitworth thread, maybe it is a "Truncated Whitworth" thread?
Any machinists from the Old Blighty on here?

06-04-2012, 07:44 AM   #5
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The easy way: Don't bother machining. Use a body cap -- I'll use M42 body caps for narrow-base lenses, a thick black generic PK body cap for those with wider-bases. Just gouge-out a hole into which to jam|thread the lens. Other mount adaptations involve macro-tube sections and glue.
06-04-2012, 08:11 AM   #6
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A few years ago I used an epoxy casting kit purchased at a model aircraft/hobby store to make a batch of DIY body caps. The process uses a latex-like material to make a mold and an epoxy-plus-filler liquid to cast the parts. Dimensional stability and detail in the cast parts was excellent.

While I didn't try it, I believe it would be feasible to include existing metal components as part of the casting in such a manner as to combine threaded sleeves that would otherwise be difficult or impossible to machine from scratch. I can see using this technique to fabricate lens/body adapters where heavy use and durability aren't a high priority.

The process was much like setting up to cast with metal in so far as making sure the latex mold could release the 3-dimentional casting. A review of metal casting procedures was a great help.

H2
06-04-2012, 08:31 AM   #7
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QuoteOriginally posted by wombat2go Quote
Not that it matters for lenses, but the American inch is different to the British inch, and those Canadians later caused another inch which is different again
There are many things which divide the English-speaking peoples,
but AFAIK, the inch is not one of them.
06-04-2012, 09:08 AM   #8
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Yes, lyt
There is not much info on internet about it
It looks like at one time the british inch was 24.40005 mm
the american inch was 25.39996 mm
In the 1960's the inch was changed to be 25.40 mm across the world, pulgada etc
It would be interesting to know if the Leica M39 ever changed ( the differences are so small that it does not matter)
My South Bend lathe is from 1936. Fortunately can cut the Leica M39 whitworth mount, but a modern metric lathe can not, without modification.
On the other hand, my old USA lathe can not cut a metric lens thread without adding an expensive gear set.
that is what I found so far, still reading about it. It looks like camera threads are still often based on the British whitworth standard

06-04-2012, 10:01 AM   #9
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QuoteOriginally posted by wombat2go Quote
It looks like at one time the british inch was 24.40005 mm
the american inch was 25.39996 mm
The book "Workshop Calculations, Tables and Formulae," F. J. Camm,
published in London by George Newnes Limited in the late 1930s,
identifies a yard as 0.914399 metre [sic] on page 46.
Since 914.399 / 36 = 25.39997222 . . . ,
that would make the British inch essentially identical to the American.

BTW, that book identifies 26 threads per inch as a "standard brass thread."
I believe that plumbing fittings still use that, with the 55 degree angle,
so it shouldn't be too hard to find the right tool.

British standard brass thread - Wikipedia, the free encyclopedia
06-04-2012, 12:50 PM   #10
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Thanks lyt
I found and ordered on rdgtools.co.uk the preformed tools needed, for the 55 degree whitworth threads on the M39 and 6mm shank should fit in the 1/4 ' toolholders here.

M39 is 26 TPI is 0.977 mm, not quite 1mm

I have machined the M4/3 bayonets quite OK, about to try making the K bayonet.
06-04-2012, 12:54 PM   #11
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Sounds good. Let us know how it "turns" out.
06-04-2012, 02:18 PM   #12
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QuoteOriginally posted by pacerr Quote
A few years ago I used an epoxy casting kit purchased at a model aircraft/hobby store to make a batch of DIY body caps. The process uses a latex-like material to make a mold and an epoxy-plus-filler liquid to cast the parts. Dimensional stability and detail in the cast parts was excellent.

While I didn't try it, I believe it would be feasible to include existing metal components as part of the casting in such a manner as to combine threaded sleeves that would otherwise be difficult or impossible to machine from scratch. I can see using this technique to fabricate lens/body adapters where heavy use and durability aren't a high priority.

The process was much like setting up to cast with metal in so far as making sure the latex mold could release the 3-dimentional casting. A review of metal casting procedures was a great help.

H2
Good suggestion.
I bought 63mm dia by 300 mm lengths of solid 6061 aluminum and Delrin (Acetal high density plastic) - about $40.00 each
(repost) https://www.box.com/s/07fbf8f82e37f9505ac6
As a PK lens housing is mostly hollow there is a lot of waste.
06-11-2012, 01:59 PM - 1 Like   #13
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I got a set of Pentax 110 lenses 18mm, 24mm and 50mm, all 1:2.8 plus AF100P flash for $45
They cleaned up quite OK.
So I made a P110 to M4/3 adaptor
https://www.box.com/s/2c50027b4ffaab6eb0e2

Each lens will have a sleeve which is interference fit in the M43 side.
Putting a lens on involves adjusting the sleeve to register at infinity focus then tighten an internal grub screw.
https://www.box.com/s/481afc72c76949b81878

These lenses have no aperture adjustment as it was in the P 110 body, so I will make a set of waterhouse stops which will be a press fit inside the sleeves.

Waiting for this to be done and the arrival of some better low reflectance paint, I took some with the 18mm wide open
https://www.box.com/s/e261fcb7b5064bc0bd71
https://www.box.com/s/8d1f6eb6b6cecf68d686
Oh, No ! the 18mm is maybe sharp enough in center but blurred at the sides of the M43 sensor . Top and bottom are not so bad.
Maybe the lens is too wide open without any stop, or maybe it is not designed for image circle of M43.
I suppose I will find out when I make the first waterhouse stop down. I will try f/6.4 first that is a 2.8 mm aperture.
Anyway I can change the Oly aspect ratio to 1:1 and just use part of the sensor if the lens is not improved when stopped down.

The PK M43 adaptor I made previously gives good results,sharp right across.
This is the PK adaptor (posted previously) with a big old zoom good for movie mode.
https://www.box.com/s/7aae97f349d2c1bf0cf3


Making the M43 P110 adaptor:
Starting with the billet
https://www.box.com/s/75c2150a90a30988ef2b


Boring the register adjusting sleeve
https://www.box.com/s/4890fa930e77bad40a9d

Marking out the bayonet profiles 1930's style etc to copy a M43 mount cap.
https://www.box.com/s/1132212721ee4b524730

Hand shaping the bayonet reliefs using a die grinding burr
https://www.box.com/s/a42bfb9fca25c12fb269

Last edited by wombat2go; 06-11-2012 at 02:18 PM.
06-12-2012, 10:25 AM   #14
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Further on the above on the P110 to M43 adaptor.
I made the first Waterhouse stop from acetal that is press fit, mounted 0.7 mm behind the rear element of the P110 lenses.
First thing, I had to machine a 40 degree angle on the thickness to minimize vignette caused by the stop on the M43 corners.
With a 27mm register and 21mm wide to sensor corner the light has to bend about 40 degrees to reach the corners of the sensor.

This first stop has a 6mm hole so Pentax-110 18mm it is f/3, 24mm f/4, and 50mm f/8

With the Waterhouse, the corner sharpness on the full sensor is much better. The 18mm is best but still has noticeable softness on the corners. The Oly can be set for 1:1 aspect ratio when using the 24mm and 50mm.

The M43 sensor is almost same as the original Pentax 110 (13 by 17mm) so I wonder if the original film camera was also a bit soft in the corners? I suppose the camera was not intended for the 19 inch print width that I am looking at on the Eizo.
06-12-2012, 08:05 PM   #15
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https://www.box.com/s/73bfb644482b0704aef9

I am about to try this for the metal and plastic parts inside the homebrew adaptors. I saw ref to it on an optical lab forum.
The sensors bounce light back to the lens more so than the film did, I think, leading to flare etc.
Also we tend to take low light high iso shots with bright lamps windows etc, that would have been flash shots with film.
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