WTB:Process lens, (Germinar, Tessar, Ronar, Saphir, RDA, Cooke, 30" to 72 inch UULF

[Asher Kelman]

I'm looking for lenses for my walk in camera obscura. So please let me know what you have available.

I have so far a 760 app Nikkor

a 1000 mm Zeiss Germinar, if it will arrive!!

now looking for longer lenses!

PM or email to editor.opfATmac.com

Asher

[Asher Kelman]

If you don't have a process lens, then an XXL would do too, LOL!

Come on, go through your boxes and drawers. Where's the wide coverage/huge monster lens you bought for a project long forgotten?

Asher

[Asher Kelman]

Still looking! What about 70 inch or 72"

[Asher Kelman]

Maybe you have a cooke process lens or a Wray from the U.K.

Thanks for looking?

[Greg Davis]

I have a brass barrel 48 inch APO Artar that is missing the aperture blades. I had intended to have it mounted in a shutter, but I will never use this lens for anything. If you are interested, make an offer.

[Jim Jones]

A 1/4 or 1/2 diopter close-up adaptor lens with an appropriately placed aperture might provide a bright enough image for some applications.

[Asher Kelman]

A 1/4 or 1/2 diopter close-up adaptor lens with an appropriately placed aperture might provide a bright enough image for some applications.

Jim,

Are you saying to use alone? I already thought of using one with a process lens to decrease the required distance to the subject!

Asher

[ausphoto]

I have a Cooke Apochromatic 25-inch ... is that too small for your needs?

[Asher Kelman]

Thanks PM sent!

[Maris]

I have set up several walk-in camera obscura rooms by blocking a window and inserting very long focal length lens in the opaque window screen.

Making a long focal length lens is easy and cheap and the image quality is ok because the large focal ratio minimises aberrations. I get two spectacle lenses, say +3 and -3 dioptre, from my local optometrist at about $20 each. When held together the powers cancel and the focal length is infinite. When separated, positive converging power (adjustable!) appears according to the distance between the lenses. The mathematical basis is given in Gullstrand's Equation.