E F Grun 6" Focus Liquid Lens Oil Filled

[Dr Klaus Schmitt]

A rare bird indeed I would say ... 170554763656

Any experiences here?

[goamules]

No direct experience, but I've read it was a failed design attempt. A gimmick.

[CCHarrison]

more here http://www.liveauctioneers.com/item/2668551

and lots of google books on this cool lens

http://www.google.com/search?tbs=bks...id+lens&num=10


Dan

[goamules]

Thanks Dan. That was as good a description as what I'd read last time one came up:

"...the two rear elements were separated by a layer of oil in place of air. The doctor, knowing little about optics, assumed that this would improve the lens in a way similar to the way the oil-immersion microscope lens functions. It did, however, not perform even as well as a conventional Petzval lens of the same focal length and aperture. Desptie extensive initial publicity, sales were minimal and by 1903 the lens had apparently been discontinued."

"mmmm....lens with a liquid center...aaahhhh...." (Said in Homer voice)

[jnantz]

everything is a gimmick, unless you unlock its secrets.

[Nodda Duma]

Some of the best most highly sought after refractive astronomical telescopes available on the market today are oil-space apochromatics by Roland Christen of Astro-Physics.

It helps to consider the refractive index of oil in the design of the optics, which I highly doubt was done for this lens.

[LabRat]

Some less lens surface to air spaces inside???

Steve K

[Mark Sawyer]

I believe that Fram made a lens of similar construction...

[Jim Galli]

I had a Protar once that had badly crazed on one element of the 4 and it came apart in my hands. Cleaned with acetone and put a drop of Wesson cooking oil where the glue had once been, put it back together and it was wonderful. Of course that's a little different than oil becoming the entire element. :0

[Greg]

I had a Protar once that had badly crazed on one element of the 4 and it came apart in my hands. Cleaned with acetone and put a drop of Wesson cooking oil where the glue had once been, put it back together and it was wonderful. Of course that's a little different than oil becoming the entire element. :0

Recently bought, at a bargain price, a classic uncoated lens in which the front element is badly crazed. Did some research and read that you can use Turtle Wax One Step Headlight Cleaner and Sealant to clean up scratches. Has anybody had any experience using a cleaner and sealant like that on a scratched glass optic? If there is a method for "covering up" scratches, I'd love to know what it is... have seen many a lens with scratches on the front elements up for auction being finally sold for ridiculously low prices. Have read a lot of descriptions of lenses being scratched and the seller stating that the scratch "does not affect the performance"... disagree based on personal experience.