Joe Smigiel
31-Dec-2012, 20:23
I have a brass Bausch & Lomb projection lens made for the Nicholas Powers Company. It sits about 6" high and ~ 3" in diameter. I thought it was a Petzval design but it looks flipped around and the thick rear pair is not cemented although they fit together with no air space. The front pair has a metal spacer ring. It looks something like this:
http://24.media.tumblr.com/1adbb73ccbd02c2391250f800fa392a9/tumblr_mfx98g6ao21qmnn9io8_r1_1280.jpg
http://25.media.tumblr.com/81b6fc2c2b28528de5a1de65ccadb011/tumblr_mfx98g6ao21qmnn9io3_1280.jpg
The diagram in the vade mecum that seems to match best is Q4 which is a Petzval design with different-proportioned elements and a reverse order. Were any Petzvals non-cemented and is that what I have here? The rear pair is marked 28 In E.F. and focuses at ~28" as expected. The front group seemed to form an (dim) image around 40" and when combined, the lens has a back focus of about 16".
http://24.media.tumblr.com/1adbb73ccbd02c2391250f800fa392a9/tumblr_mfx98g6ao21qmnn9io8_r1_1280.jpg
http://25.media.tumblr.com/81b6fc2c2b28528de5a1de65ccadb011/tumblr_mfx98g6ao21qmnn9io3_1280.jpg
The diagram in the vade mecum that seems to match best is Q4 which is a Petzval design with different-proportioned elements and a reverse order. Were any Petzvals non-cemented and is that what I have here? The rear pair is marked 28 In E.F. and focuses at ~28" as expected. The front group seemed to form an (dim) image around 40" and when combined, the lens has a back focus of about 16".