Researching home-made lenses

[Removed Account]

This is really interesting... Are those prints regular silver gelatin, Ray? Did you use anything as an aperture, what kind of exposure times did you get? Sorry, for the barrage of questions, but it seems like this would be a great way to take shots when I get my camera, until (and after) I get a 'normal' lens.

- Justin

 

[steven_e007]

Well, I read a book with the same title, but the book I read had several photographs made with the lenses which were suggested for construction, sources for glass lens elements were cited, and somewhat ingenious use was made of ordinary plastic plumbing pipes--with some use of foam core, but not foam rubber. The only thing I found suspect was the suggestion of black construction paper for making Waterhouse stops--surely the thing to do would be to drill holes in thin metal stock. With a little effort he could have provided drill bit diameters for f/stops of various sizes for each lens, and the results would have been far more substantial.

I stand corrected. After reading my copy of the book again there is
just one photograph (figure 3.7 on page 95) which uses plano-convex lenses mounted in a pvc tube. It is a very soft and heavily vignetted image.

There are a couple of other pictures which were taken in 1999 using a 'landscape lens'. But it doesn't say this is a home made plastic pipe version and I suspect from the f number details given, and the way it was stopped down mid exposure, that this is probably an original 19th century brass mounted lens.

May be you have a different version to me, but my book contains no examples of pictures taken with any of the other, more complex, lenses at all. I suspect this may well be because the lack of engineering accuracy inherant in plastic pipes and foam (core / rubber - I'm not sure what the difference is...) probably introduces errors and abberations that are much greater than the design is trying to correct and results are probably very poor. Maybe fun, maybe educational, but I doubt whether these techniques could produce anything most of us would want to use.

I think with the sort of focal lengths we are looking at we probably need to be thinking of working to accuracies of quite a lot better than 1mm to mount lenses, plus everything needs to be centred on, and perpendicular to, the opitical axis.

I think this dictates aluminium or brass, a lathe and someone who knows how to use it. But these are not difficult to find, I'm sure good useable lenses are within the scope of anyone who can access such skills.

Steve

 

[Ray Heath]

... I think with the sort of focal lengths we are looking at we probably need to be thinking of working to accuracies of quite a lot better than 1mm to mount lenses, plus everything needs to be centred on, and perpendicular to, the opitical axis.

I think this dictates aluminium or brass, a lathe and someone who knows how to use it. But these are not difficult to find, I'm sure good useable lenses are within the scope of anyone who can access such skills.

Steve

g'day all

Steve, your probably right if the intent is to make a 'perfect' lens, but that is certainly not my intent and does it need to be?

i can see some aesthetic beauty in the less than perfect

 

[steven_e007]

g'day all

Steve, your probably right if the intent is to make a 'perfect' lens, but that is certainly not my intent and does it need to be?

i can see some aesthetic beauty in the less than perfect

Oh, with the best will in the world I think a home made lens even using amateur engineering skills, especially if we try to grind our own glass, is going to be a lot less than perfect!

This puts us in the class of the early victorian amateurs at best and I'm sure our home made lenses would be full of interesting aberations!

Professionally made lenses even in Victorian times will be made with a craftmans precision which I think we would fall very well short of without a good engineering and optical apprentiship behind us. I have a fair collection of 19th and early 20th Century optics and they are beautifully crafted pieces of optical engineering, no way would I presume to replicate even the simplest Rapid Rectilinear.

I suppose it depends what we are trying to achieve. Personally I gained a lot of satisfaction from building my own camera. I'm sure I would gain the same satisaction from building a lens, but I would want to build it to the best of my ability.

As for taking interesting photographs with 'unusual' optics, I think Richard Dawkins experimented with plastic bags full of water in front of a camera to demonstrate how an eye can evolve in simple stages (<Plastic bag + water> represents <Thin membrane + cell sap>). He was able to demonstrate some degree of focussing to produce an image very easily. I'm sure there is scope for experimentation, here.

Actually, water filled glass vessels have been used as camera lenses in Victorian times. There was that Thomas Sutton wide angle camera? I wonder what sort of aberations that produced!

Mirrors have also been used and are easier to make than lenses. Some amateur astronomers do grind their own mirrors, but I'm sure if you are not chasing high optical quality there must also be scope for casting mirrors in resin or plastic and 'silvering' with metal paint that can be polished. I bet very big mirrors could be made this way which would be impractical to grind from glass. I've seen a drawing of a Daguerrotype portrait camera that used a huge parabolic mirror. I bet this too gave 'interesting' images!

But, if making the lens is not a priority, there must be a wide range of objects that could be used to make an image. Shaving mirrors, magnifying glasses, crystals, parabolic reflectors from lamps and torches. I can even focus an image of the lightbulb above me with the base of this wineglass I'm holding!

(Hic).

Steve

 

[Jim Noel]

Holy cow Jim, how big was it? How was the image? Thanks everyone for your advice, I think I will give making a lens a shot when I build a camera, but for now with my first forays into 4x5 I will stick with cheapies I can dig up...

The diameter as I remember was quite small, about 3-4 inches. The effective aperture was in the neighborhood of f 64 -90, so exposures were quite long, especially at night with Super XX film.

I wish now I had been able to hang onto that lens as it would be a lot of fun to use it again, but alas, it is long gone, as is my old Graflex.

 

[Murray@uptowngallery]

Mr. Heath, et al:

Have any of you experimented with homebrew symmetrical lenses?

I'm interested in the dynamics of the stop position.

For cafeharrar, one problem I have with the optics software programs is most surplus optics have incomplete data.

Anyone comfortable discussing scaling of lens formulae from such software previously mentioned? I know they scale proportionally to f.l. from whatever the reference design is (50 or 100 mm?), but I got confused figuring positions...from the stop or from front/rear?

There is a guy who appears rarely on rec.photo.equipment.large-format, Brian Caldwell, who wrote the Lensview software. He designed and ground his own 11x14 format Topogon (very similar to as Metrogon), had the glass slowly crack after cementing, and made another. He's kind of like a unicorn, appears rarely, and dispenses a crystal of profound and practical wisdom, then he's gone. His website is never up when I try and he doesn't answer contacts...he usually appears with friendly corrections to incorrect technical statements posted.

Anyway, can't find him, so I'm trying here for fellow experimenters

 

[Mustafa Umut Sarac]

mirror making technology

Hello Steven , I think if you want to make big parabolic mirrors for whatever the reason , you can experiment with new technologies.
You dont need to find , buy , cut big , thick and expensive special glasses.
There are two ways , first you can buy aluminized kapton thin film and build a pressurized mirror out of it.
basically all you need is a box , one side is closed with kapton film and lower the pressure inside of the box. Film will become the shape of parabolic mirror.
AFRL made several successful tests with this material and future space mirrors will be constructed out of this film. But you have to be sure about that do kapton metallic surface satisfy you or not. If not , you can contact with afrl and get contact details of their telescope mirror quality coating service.
Now I will explain two inventions from me , i did not see anything anywhere about them until today.
You can make a pressurized mirror with the help of thin film and load the surface of the film with slow curing , less shrinking , less heat producing polymer. By this way you can mold the mirror. You can brain storm with the idea.
Second idea is similar but using a liquid. You can fill a cup with liquid mercury and you can rotate it for the parabolic shape. Than you can pure thin epoxy layers on to the liquid mirror for to mold it.
I think flat mirrors could be loaded to the film holder of big format cameras and inside a digital camera could record it i m not sure the dobility of it but an idea.

Best ,

Mustafa Umut Sarac

Mirrors have also been used and are easier to make than lenses. Some amateur astronomers do grind their own mirrors, but I'm sure if you are not chasing high optical quality there must also be scope for casting mirrors in resin or plastic and 'silvering' with metal paint that can be polished. I bet very big mirrors could be made this way which would be impractical to grind from glass. I've seen a drawing of a Daguerrotype portrait camera that used a huge parabolic mirror. I bet this too gave 'interesting' images!

 

[Mustafa Umut Sarac]

DIY LENS GRINDING

This is the best post I have ever seen in the apug . Nurray , can you write whatever you know about homemade grinding to tight tolerances , measuring and any other experiences of mr. caldwell ?
Is there a site which explains diy lens grinding ? Do schott sell small amount of glass ? I am sure some japanese friends tried this ? Where are they ?

Mr. Heath, et al:

There is a guy who appears rarely on rec.photo.equipment.large-format, Brian Caldwell, who wrote the Lensview software. He designed and ground his own 11x14 format Topogon (very similar to as Metrogon), had the glass slowly crack after cementing, and made another. He's kind of like a unicorn, appears rarely, and dispenses a crystal of profound and practical wisdom, then he's gone. His website is never up when I try and he doesn't answer contacts...he usually appears with friendly corrections to incorrect technical statements posted.

Anyway, can't find him, so I'm trying here for fellow experimenters

 

[Murray@uptowngallery]

I know nothing about grinding other than flat thing like ground glass...DQ/Image Maker made one once.

That is about all I know about Brian C...he has helped me out with questions but one never knows where to find him.

 

[Mustafa Umut Sarac]

diy homemade lens grinding book file attachment

Hello , I attached a book downloaded from archive org .
You can find pdf version at
http://www.archive.org/details/lensworkforamate00orforich
Lens-work for amateurs
Orford Henry
1912
Its subject
diy do it yourself lens grinding book for amateurs
There are other lens grinding books :
Lens Design Fundamentals" by Rudolf Kingslake
http://www.lindsaybks.com/bks/expphy/index.html
and interesting site for amateur for to measure the spherical surface of the small lens :
http://www.users.bigpond.com/PJIFL/page5.html

Best ,

Mustafa Umut Sarac

 

[AgX]

Mustafa,

I like that idea with that centrifugal mercury mold.

But referring to that foil mirror formed by negative pressure: Would you not rather get a spherical than parabolical mirror?

 

[Lee L]

But referring to that foil mirror formed by negative pressure: Would you not rather get a spherical than parabolical mirror?

You want a parabolic mirror because of spherical abberation: Dead Link Removed

Mirrors of f:8 or longer f-ratios can perform reasonably well for visual work if spherical, but faster f-ratios and critical imaging require a parabolic mirror for best results.

Lee

 

[Mustafa Umut Sarac]

Ferro Fluids and making lens molds from them

Hello , As you know , lens grinding technology changed too much since the mid 90s and lens making shops using new toys. At this new technology , they are using a metallic head with a magnetic winding inside and they are using magnetism to form a fluidic surface on the metal head with the help of ferrofluids and abrasive powders.
This ferro fluid and abrasive powders running on the metal head from one side to other and pumps sucking and injecting this fluid. And ferrofluid and abrasive mix interact with glass or plastic and gently grind it while glass rotating with high speed. This is highly complex and extreme hard to realize technology.
I think ferrofluids could be used for to make harder molds than the rotating mercury. This is open to brain storm.
And how can we reach to Brian Caldwell ? And is there anyone who constructed his own lens with grinding for to tell the story?

Best ,

Mustafa Umut Sarac

 

[AgX]

You want a parabolic mirror because of spherical abberation

Lee, you misunderstood my question/remark: I know of that aberration issue. I was referring to the mechanics of suction forming. To my understanding one would get a spherical result and not a parabolic one. Please correct me if I'm wrong.

 

[AgX]

Mustafa,
this ferromagnetic grinding is new to me. From what I understand from your post it is used to make grinding more effective than with a standard paste. I do not see any form of electrical shape steering involved.
However your idea of electrical controlling the shape of ferromagnetic fluid/viscous molds seems very interesting. At first sight It gives you the chance of deliberately and immediately controlling the shape. In contrast to cutting a mold on a lathe. However, on a lathe you will know in advance what form you will get. With this electrical mold, I guess, one would either have to employ a delicate coil system with known algorithms to predict the form of the resulting mold or steering the coils by trial and error, using a scanning technique to measure the mold or just molding lenses and see how they look.
It might seem to you that I am spoiling your ideas, but to me, for amateur use, the lathe used to make a mold would be more economical.

But, and it is a pity that you don’t react on my replies to your postings, what about grinding a lens on a lathe, as asked before?
For the projects, I guess you have in mind, one would rather need single lens elements not multiples of them and thus not necessarily a mold. You stated that you have access to a CNC lathe. If you could get hold on a piece of raw optical glass of the needed composition and size, what could form a problem, you could mill it to size, put it on the lathe and start grinding. More convinient (and economical?) would be to use a lens from a supplier of optical elements of the right composition and a bit oversized. Put it on the lathe and grind and polish it there.
I admit I have NO experience in optical grinding whatsoever and thus do not know whether this lathe-grinding is really workable. If so, there should be companies around which offer custom grinding of single lenses. This of course will take us off the DIY way…

 

[Lee L]

Lee, you misunderstood my question/remark: I know of that aberration issue. I was referring to the mechanics of suction forming. To my understanding one would get a spherical result and not a parabolic one. Please correct me if I'm wrong.

Sorry. It was the placement of the word "rather" in the sentence that got me. I'm not familiar with the suction forming method, so can't answer that. Spin casting, as you probably know, results in a parabolic mirror.

Lee

 

[Mustafa Umut Sarac]

diy homemade parabolic mirror with mercury mold and cnc glass

Dear AgX , Thank you for your message and interest to my ideas.
First of all , lets start the first mail about rotating mercury. This technology is a promising way for the astronomy schools who has not money to build 6 meters diameter mirror. The weak side of the liquid mirror is thay you can not move the mirror and you have to move the ccd camera on the parabola.
I saw somewhere , the real problem is the dust. You are building a liquid mirror at a mountain , you are opening it to nature and all things flying is dirting the mirror.
For to protect the mirror , researchers coat the mercury with thin layer of epoxy. I thought this layer could be used as a mold .
You have a 6 meters wide mirror , hard and ready to be aluminized.
I think this is the most basic form of creating giant telescope. Well even making 80 cms mirror is a giant experience for the amateur and the wallet
Well I am one who has limited money to do expensive things and i have a hunger eye for them also. So I am developing cheap solutions.
One can quickly produce with a rotating mercury mirror , a lots of plastic mirrors . All you have to have a low shrinking , less heat producing , fastcuring , hard plastic. This can be acrylic formulas with UV curing forms.
diy homemade parabolic big wide diameter telescope mirror centrifugal rotating moving mercury quicksilver mold
I think magnetic fluidss are so interesting , they can be used to change a form . Nowadays I am thinking to cover the americas boat critical surfaces with biomimic or laboratory generated surfaces , may be at the future , ferrofluids will be used to change the form of a formula car at high speed or at curves. I think to look at this magic material as a new tool is a more satisfactory way. I mean open your mind .
I think , if it is possible to grind a lens at a cnc lathe , it could be very cheap , i worked a company which produce aluminum parts and i saw many cnc generated parts at there . They had have to polished by hand because cnc lathe was not producing excellent clean parts. But i know some cnc lathe parts are excellent at the industry magazines.
I think you have to find few cnc shops telephones and call them.If I am not wrong you are at germany and germany produces best cnc lathes in the world. For to make your research easier , i think you have to find a cnc shop near to wetzlar leica factory . i think they will have a answer.
This is a good question But there is also one thing , if you want to produce precision parts with a cnc lathe , you have to calculate the heat and vibration of the toolings. This is more important at the glass also and if you want to use high refractive index glasses , they are very soft and very hard to cnc if i m not wrong. What about the tolerances ? How will you produce exact curve - from your lens design software results - with the cnc lathe.
You have to know what cnc can do and what lens design software can advise.
I had been found a web site from usa which produces plastic lens prototypes with cnc but they were aplying a special polishing after all , if i am not wrong a flame !
If you can find a glass lens cnc shop , please write here.
And now I thinked , may be rotating molds can be made by molten tin or molten pb !

Best ,

Mustafa Umut Sarac

Mustafa,
this ferromagnetic grinding is new to me. From what I understand from your post it is used to make grinding more effective than with a standard paste. I do not see any form of electrical shape steering involved.
However your idea of electrical controlling the shape of ferromagnetic fluid/viscous molds seems very interesting. At first sight It gives you the chance of deliberately and immediately controlling the shape. In contrast to cutting a mold on a lathe. However, on a lathe you will know in advance what form you will get. With this electrical mold, I guess, one would either have to employ a delicate coil system with known algorithms to predict the form of the resulting mold or steering the coils by trial and error, using a scanning technique to measure the mold or just molding lenses and see how they look.
It might seem to you that I am spoiling your ideas, but to me, for amateur use, the lathe used to make a mold would be more economical.

But, and it is a pity that you don’t react on my replies to your postings, what about grinding a lens on a lathe, as asked before?
For the projects, I guess you have in mind, one would rather need single lens elements not multiples of them and thus not necessarily a mold. You stated that you have access to a CNC lathe. If you could get hold on a piece of raw optical glass of the needed composition and size, what could form a problem, you could mill it to size, put it on the lathe and start grinding. More convinient (and economical?) would be to use a lens from a supplier of optical elements of the right composition and a bit oversized. Put it on the lathe and grind and polish it there.
I admit I have NO experience in optical grinding whatsoever and thus do not know whether this lathe-grinding is really workable. If so, there should be companies around which offer custom grinding of single lenses. This of course will take us off the DIY way…

 

[AgX]

-) any centrifugal mirror, or in this case mold, would produce a parabolic surface.
Something rather scarcely used in general photography. Here one rather needs spherical or a-spherical lenses (Yes, parabolic surfaces are a-spherical ones too. Though I don’t think those a-spherical lens elements found in photo lenses are parabolic. Schematic sketches of those show something different.

-) Concerning your idea of electrically controlling a mold shape formed by a ferromagnetic fluid/paste, have you got any idea how that could be achieved on amateur scale? I can’t imagine it could be anywhere in the region of precision a lathe could do on a mold or the glass itself, and I am putting it mildly.

-) Concerning working with a lathe it could be a problem that a grinding tool made of silicone carbide would deform rather faster I guess than a sintered metal tool on a metal subject. (Diamonds are a guy’s best friend.) Polishing should also be possible by attaching a polishing pad on the lathe which runs alongside the glass surface as did the grinding tool before. (Though this could result in circular marks and I am not sure how difficult it would be to keep within tolerances with this polishing method. But as the earlier a-spherical lenses were worked on by hand…) One has to keep rinse water and later polishing fluid running over the lens, something the lathe won’t like. But one should be able to arrange the whole thing in a way that there is room for some sort of basin that keeps the lathe clear of all that abrasive stuff.

Finally it should be stated that there are several reasons to participate in those threads: pure theoretical interest in what is feasible technically; interest in playing around with lens making; interest in playing around with off the mainstream lenses. In the latter case it can be that rather high demands on the lens quality are made.

 

[Murray@uptowngallery]

Interesting, but I guess the guys interested in assembling a lens for a camera are adrift on a raft now.

 

[Struan Gray]

If you are interested in spin-casting of large mirrors, the Mirror Lab at the University of Arizona has a lot of pictures online. They made the mirrors for the Large Binocular Telescope and Magellan Telescope projects in this way.

http://uanews.org/cgi-bin/WebObjects/imageBase.woa/1/wo/zamFdYgNNKwWrgrJnCN3sg/0.3
(Click the search button - I couldn't find a direct link)
http://www.astro.virginia.edu/class/oconnell/LBT/

Somewhere on the web is a video of the furnace spinning, but I couldn't find it in a quick and dirty search.

This technique could be used on a smaller scale, but it is worth bearing in mind that these telescope mirrors are polished and coated with aluminium after the spin-casting process, and it is these latter steps that give them good optical performance. If you plan to rely on the parabolic shape alone, you will not come close to a good spherical lens.

In any case, the ideal non-spherical surfaces to make images of objects closer than infinity are elliptical (I think it was Descartes who proved this). Unlike with spherical surfaces, there is no straightforward way of generating an ellipse that is mechanically accurate enough to be used as-is without further polishing to refine the figure.

Direct machining of optics with diamond tools is done, but the figures you can produce are currently only good enough for IR wavelenths. If you want a surface smooth and accurate enough for optical light you need to fine-polish after the coarse figuring has been done on the diamond lathe.

None of these techniques are suitable for any 'home builder' worthy of the name. Just a bearing accurate enough and sufficiently jitter free to do spin casting or make a diamond optical lathe is going to cost significantly more than a very complete set of LF lenses. You would have to *really* want to do this for yourself.

For me, homemade lenses should be an end in themselves. When you can buy complete, coated process lenses for a few tens of dollars they are not even a way to save real money - except perhaps in the very long focal lengths. If you stump up the cash, Leitz will sell you a precision mill for making aspheres 'at home', and even train you how to use it, but most people rich and leisured enough to do that can easily find better uses of their time.

 

[Murray@uptowngallery]

Yah, process lenses of less-than-cult status and short to mid f.l. are easily attained...no one 'serious' much likes the Agfa-Staebel-Ultragon-Helioprint or apparenty Ilex PROCESS Paragon (regular Paragon are liked) class of process lenses, but after a few years of pinholing, they should do fine for me and cost far less than Rodenstock, Schneider and Nikkor options. I don't care about fitting in a shutter. Pinhole has trained me to live with long slow manual shutter action.

I'm not interested in making a plasmat or planar or whatever the 6-element APO ones are called (acquisition covered above).

I'm interested in lenses with personality but don't need a 400 mm Petzval or 50 mm LF wideangle badly enough to pay market price, so I'll experiment (perhaps miserably) with some Surplus Shed stuff. I'm well aware of what I don't know, but still want to be SOMEwhere near ballpark to start...

 

[Mustafa Umut Sarac]

Murray , I think you are new to downloading , experimenting , uninstalling and redownloading headache on optical softwares. If you look to the lens database of these softwares - there are few free softwares at google - you can find hundreds of lenses which are ready to use with other lenses. I mean with lens word that single element glass . There are billions of possibilities to construct a final lens with them. I think the best way is to ask these single , double , triple glass manufacturers for to create best possible mix.
You can download zemax demo and search these lenses.
Primary manufacturers
HOYA
SCHOTT
CORNING
PILKINGTON
HIKARI and others.
You can contact with them and ask them to construct a lens from their products for you. PENTACON have a service for that and you can contact with them.
And OSLO , I became their list member two years ago and ask them to construct a lens with the cheapest glass or plastic.
Answer was to use two 10 or 12 diopter eyeglass lenses back to back.

Best ,

Mustafa Umut Sarac

 

[Mustafa Umut Sarac]

http://www.schott.com/optics_devices/english/download/index.html
Murray , look at this

 

[Ole]

Answer was to use two 10 or 12 diopter eyeglass lenses back to back.

... or 2 or 2.5 diopter, if you want a focal length around 200mm to try on an LF camera. The fun thing is trying to optimise the spacing - and that's where the software comes in.

 

[AgX]

Struan,

many thanks on commenting on these thoughts on home made lens element, especially on the bearing problem; I would like to reply on this with a pun, bit it only works in German: I thought, "daß verschleift sich schon"...

And on software: such a software is to be downloaded for free from Linos (and Edmund?), they even recommend it to their customers.