grinding my own lens ? grinding my own lens !
might seem a bit far fetched but I've only been at this site a little while and have learned so much, no question unanswered yet - so I'll have a go with this:
Any advice/tips/starting points on how to go about grinding and polishing my own lens ?
... like I guess the old astronomers would have had to ...
some sort of lathe ? and then months of polishing ?
probably a maths degree ?
I dont want to make a super correct lens, and dont expect to be able to understand centuries of design in one go, but it would be nice to attempt to make one using the original old old (old) method/s
I know an educational institution in Leiden, Netherlands, where they have a deparment for people like you. It's called fine optics - and you only get admitted after severe selection, as we were told by the head of this department...go give it a try. Maybe you can get funding as a kind of 'back to school project'.
Originally Posted by Rock Poper
The astronomy guys do it all the time. Do a google search for it. However, the quality they need for viewing is pretty far below what most of us would consider acceptable for film. Most of us. I looked into it and wisely got over the urge. The astro folks say they can do it over the course of a few weekends. Longer lens typically have a shallower curvature, so that makes sense. Trying to makea wide angle would probably take a LOT longer, and be less forgiving. I keep thinking someone should be able to make a hypergon-clone at a reasonable cost. It's only two elements. Surely there's a suitable optical plastic that could be easily molded.
~certainly if you'd outsource it to a Chinese partner. The Chinese just love copying things. Question is: where to find a reliable Chinese partner. You could set up a program for copies of all desired lenses, and start out with a top ten of the most wanted...
Originally Posted by Terence
Oh boy, my entrepeneurial genes are certainly in full flight today.
Didn't Wisner try this - and give up?
Originally Posted by Terence
The inside curvature is too deep for automatic grinding, I think. So maybe the Chinese could do it by hand
I just got hold of Rudolf Kingslake's "A History of the Photographic Lens", an interesting read for anyone into this sort of stuff. If you want to avoid cementing lenses (or antireflex-coating them), the Steinheil Periskop and Zentmayer hemisymmetrical would be the easiest to get anywhere near decent results from. After those a Cooke Triplet, perhaps?
-- Ole Tjugen, Luddite Elitist
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Aren't most aspherical elements in modern lenses simply molded anyway? Shouldn't be too hard to mold those hypergon elements... the fact that they are symmetrical makes it even simpler !
People could then buy all the hypergons they dream about and realize how much the wide-angle lens design process has improved over the last 150 years !
But then again, there are no modern lenses that go that wide...
Patrick Jan Van Hove
"The heart and mind are the true lens of the camera"
, The Ultra-Large-Format photography homepage
As one who has made a telescope, including grinding, polishing and figuring the parabolic primary mirror (starting from a cast Pyrex blank), I've got a little idea what goes on. Yes, making lenses is well within reach of amateurs. No, you don't want to start with lenses -- optical glass is expensive. Start with mirrors -- the techniques are the same, and you can work with plain soda-lime float glass (i.e. window glass) in thicker sizes, which will save you a lot of money. What makes lenses trickier than mirrors are that they have to be made from a particular glass (to have the correct index and dispersion), with pretty exact control of surface curvature, centering, wedge, and thickness, usually with final figuring based on optical testing because it's impossible to measure the surface accurately enough by any other means. Often it's necessary to make a number of other optics (which can often be reflective, and so require only a single perfect surface without constraints on those other qualities, and can be from nearly any material) just to test the one you're working on.
Even very experienced amateur opticians blanch at the thought of making cemented surfaces, but some of them have done it; there's nothing that would prevent a dedicated amateur from making a copy of a Tessar, Doppel-Anastigmat, or Rapid Rectilinear if so inclined.
Machines are often used, but they bear more resemblance to a potter's wheel than to a lathe in most cases, at least for astonomical optics (though very small lenses have been ground on machines with horizontal spindles).
The time factor is tricky -- you might well spend only 10-20 hours actually grinding and polishing each surface of a lens, but intersperse that with two or three times as much time making test equipment and testing in order to bring the lens to the correct final prescription. Add to that the cost of suitable pieces of certain exotic glasses needed for achromatizing and aberration correction, and things quickly get ugly, even if you can find the necessary information to duplicate the prescription for a particular lens.
If you want to design your own, then you add the complications of obtaining and using suitable software that can correctly deal with multiple elements and glass types; OSLO is the only package I'm aware of, and the full version is comparably priced to an industrial CAD/CAM package. There's a trial version, but it may be too limited to deal with deep curves or more than two or three elements.
Coating a lens isn't out of the question -- I read somewhere (can't remember now if it was on APUG or the Camera-Fix list) that there is a Ukrainian service that will multi-coat loose glass for quite reasonable prices, including strips and recoats of existing lenses (the tricky part being you have to remove them from any cells before shipping); there's speculation they're piggybacking on the coating equipment at the Arsenal optical factory. This would be a perfect way to get a one-off handmade lens coated. Cement first, please...
Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.
While not home polishing I did find this company when doing a search to see if the UK based Ross Company was still trading.
Wonder if they are any use to any of us ?
As much use to those of you in the UK as Edmund Industrial Optics, formerly Edmund Scientific, is to us in the US. I live a couple of miles from Edmund, get the catalog, visit the suplus shop from time to time. So far all I've found that's obviously useful for any of my photographic gear projects is adhesive-backed flocking paper.
That Ross site looks interesting... Make your own petzval portrait lens?
I have OSLO Edu - the trial version. The limitation is six surfaces, so you can calculate a triplet or half a Dagor (up to 5 cemented elements), but not a Tessar or a dialyte
-- Ole Tjugen, Luddite Elitist