Petzval Formula DIY?

[Drew Bedo]

There is a long thread here about DIY Cook Triplet projects.

What about creating (re-creating) a Petzval design? Are stock lens elements available commercially that could be assembled into a functional Petzval formula lens for LF use?

If not stock, off-the-shelf glass, can they be done by a optometrist from blanks for eye glasses?

[Oslolens]

Recommend to try. An achromat and two singles. Did some testing, but not happy with -3 and +2-something. https://www.ebay.co.uk/itm/TRIAL-LEN.../303508275135?

Edit:"not" and added: So much easier to make an anastigmat: Two diopter pointing from each other. I got a 14" Ektar where I unscrew the lens cells to use other glass. The threads are close enough to 72mm to screw on filters. I have two sets of +2 Bronica, no-name and Canon 500D to make comparable focal length, testing still not done except to check there is gathering of light

[Tin Can]

Some make 8" telescope mirrors by hand

Make a big 8" lens here

https://gotgrit.com/

[Drew Bedo]

What about the glass itself? Some elements were Crown Glass and others were Flint glass formulas. Its not just the shape of the indevidual elements . . . .

[goamules]

You are asking if materials are important in a design?

Yes, the refractive index of each lens was highly important, and slightly variable. So even if you have the precise curves mapped out for one Petzval, that is what the grinders did to be optimal for THOSE two indices. They varied the grind by the exact refraction of that particular chunk of glass. And they confirmed their grind by using optical tools, as they did the work. That's why if someone makes the mistake of slapping a part from one lens into another from this era, the results may not be as good as the original.

One can build a bridge, guitar neck, or lens from any materials on hand, but it may not work out very well. Optical science is....a science.

[Drew Bedo]

Right!

I have seen stringed instruments made from a cigar box.

If this was optimum, Gibson would do that.

[reddesert]

If you like experimenting, probably the easiest thing to do would be to get some achromats (cemented crown-flint doublets) and experiment with different combinations of focal lengths and spacings of two achromats. A pair might make an okay rough approximation of a Rapid Rectilinear - a relatively slow, symmetric combination of two doublets. Since they are achromats the chromatic aberrations are mostly taken care of. One also needs to be prepared to let the off-axis performance be sacrificed, since the usual degrees of freedom an optical designer has are restricted with off the shelf elements. One could experiment with asymmetric combinations as well, but a real Petzval is a fast lens, which increases all difficulties a lot.

I looked into DIY lens combinations while reading Jason's original thread, and as he stated, one of the issues with making a lens from stock parts is that it's hard to find much selection in off the shelf flint glass elements.

This has to be undertaken for its own reward, it is certainly not a way to save time or money. If you want to start ray tracing simple optical designs, you can try this free Java program: https://arachnoid.com/OpticalRayTracer/

[Drew Bedo]

This has to be undertaken for its own reward, it is certainly not a way to save time or money. If you want to start ray tracing simple optical designs, you can try this free Java program: https://arachnoid.com/OpticalRayTracer/

That is pretty much what I had thought. The 35mm/mirrorless Ptzval from Lomo was an industrial project.

The vintage lens are deceptively simple in construction. The glass and its grinding were the cutting edge technologies of that time period.

[martiansea]

https://gotgrit.com/

Thanks for recommending this place! I got some aluminum oxide from them to use for making a ground glass and the results were fantastic. Their prices are also fantastic.