Hand-finished Pinkham & Smith lenses?

[Petzval Paul]

Dang! I completely missed that SA on Ebay! I would have bought it. *#@^%&!

Russ,

Very interesting, indeed. So initially P&S just bought up some old landscape lenses and re-mounted them? THAT's downright incredible!

Once I took my 8 and 1/2" Darlot (my shortest Petzval) and set it up in "landscape mode" without any stops to see if it would mimic a soft focus lens. It did - to a degree. Replacing it with my Synthetic, there was quite a difference. Everything took on a glow and the highlights were positively brilliant. I could see how such a lens could be used, simply polishing in the abberations that make it all interesting.

Besides those quoted in P&S catalogs, do you know of any "names" who used the Synthetic?

- Paul

[John Z.]

I would be curious to see a few examples of photos taken with the P&S lenses, if anyone has any to post on the internet.

[Mark Sawyer]

Thank you, Russ! Wonderful information, and it does answer some of my curiousities about whether the lenses varied from specimen to specimen. Sounds like they did, and Smith, Day, and others were well aware of it. I'd still love to know exactly what they were doing to which surface by hand. It may be a secret lost to time, but it seems the folks at Cooke came close with the PS945. Then again, how do you replicate something that was unique from lens to lens? If I had a better idea, I'd be tempted to hand-aspherize a surface or two on an old B&L Tessar...

I don't know that I'd like a P & S lens more than my old Veritos, Imagon, etc., as those can produce such lovely images too. But it would be fun to try...

Again, thanks for the information. We really need a "wikipedia of lf lenses" where such technical and historical information could be accumulated. So much knowledge and lore is hiding away, waiting to be lost...

[Ernest Purdum]

Amateur astronomers hand-finish their mirrors to get rid of spherical aberration. I suppose their technique might work in reverse.

Awhile back, www.surplusshed.com had CD's with lens/mirror grinding info on them. They were "closeouts" though, so may be gone by now.

If someone wants to try something of this sort with existing lenses, I nominate the various surplus copy machine lenses as good candidates. They are super cheap and reasonably fast at f4.5. C&H Sales in Pasadena, California, may still have some. You can tell the difference between them and camera lenses because their diaphragms don't close down very far. I have no idea how hard it would be to disassemble them, though.

[Toyon]

F.C. Beach also had his "multifocal" lenses hand polished to an aspherical surface, but for another purpose - he desired to increase their depth-of-field. Kingslake writes about this in his, "Lenses in Photography," book.

[Ernest Purdum]

"Increased depth of field" is just about synonymous with soft focus.

[Toyon]

"In the soft-focus lens the depth of field is greatly increased by the abberration, which is not the case when a diffusion disk is used. Professional photographers often prefer the soft-focus lens for this reason, and because the degree of diffusion can be controlled by adjusting the iris diaphragm." Rudolf Kingslake, Lenses in Photography.

"Another way to increase the depth of field is by the deliberate introduction of axial aberration. In this way each object in the scene is imaged sharply by one zone of the lens or by light of one wavelength, while all the other zones and wavelengths produce superposed images, which are to some degree out of focus and therefore less likely to be exposed on the film. Rudolf Kingslake, A History of the Photographic Lens.

What Beach found is that one can significantly increase depth of field without introducing noticeable softness - at least at low levels of enlargement.

[Hugo Zhang]

Here is something I found a while ago...

http://www.usask.ca/lists/alt-photo-...jan05/0490.htm