O.K., how can you resist a tag line like that?
Heres the problem. I came across an old brassie at Thompson Photo (pic attached), shoved back on the shelf and I cant seem to find out what it is no markings of any kind, although it has a focusing rack on the bottom and the pinions and housing are missing. None of the designs in the Vade Mecum or Kingslake seem to fit, although it does seem to be a Petzval design maybe with the glass reversed. Here are the facts maam.
Rear cell: about 20 or 20-1/2 focal length, 2/2 constuction, concave side faces AWAY from the aperture. This face may be flat, but appears to me to be concave. This cell illuminates 8x10 although its quite diffuse away from the center as expected.
Front Cell: about 9-1/2 focal length, 2/1 construction (2 strong, 1 ghost, some minor edge separation), concave side again faces away from the aperture. This face may be flat, but appears to me to be concave. The cell again illuminates 8x10, again quite diffuse going away from center.
Combined: about 8-1/2. The combination does not illuminate 8x10 and is even more diffuse away from center than either single cell. I shot the combo using an assumption of f/8 maximum aperture and got a decently exposed neg, so the combo is tentatively f/8 give or take a stop. I figure it covers full plate at best.
The combined lens also gives some really strange triangular artifacting of highlight areas, although neither individual cell exhibits these artifacts.
I know Im probably not going to come up with a maker or year (and it isn't really important). My guess is a 9" f/5 Gundlach Petzval-design given where I found it. But has anyone seen a similar lens with similar characteristics? Do Petzvals have greatly asymmetrical elements?
Thanks!
Steve
Heres the problem. I came across an old brassie at Thompson Photo (pic attached), shoved back on the shelf and I cant seem to find out what it is no markings of any kind, although it has a focusing rack on the bottom and the pinions and housing are missing. None of the designs in the Vade Mecum or Kingslake seem to fit, although it does seem to be a Petzval design maybe with the glass reversed. Here are the facts maam.
Rear cell: about 20 or 20-1/2 focal length, 2/2 constuction, concave side faces AWAY from the aperture. This face may be flat, but appears to me to be concave. This cell illuminates 8x10 although its quite diffuse away from the center as expected.
Front Cell: about 9-1/2 focal length, 2/1 construction (2 strong, 1 ghost, some minor edge separation), concave side again faces away from the aperture. This face may be flat, but appears to me to be concave. The cell again illuminates 8x10, again quite diffuse going away from center.
Combined: about 8-1/2. The combination does not illuminate 8x10 and is even more diffuse away from center than either single cell. I shot the combo using an assumption of f/8 maximum aperture and got a decently exposed neg, so the combo is tentatively f/8 give or take a stop. I figure it covers full plate at best.
The combined lens also gives some really strange triangular artifacting of highlight areas, although neither individual cell exhibits these artifacts.
I know Im probably not going to come up with a maker or year (and it isn't really important). My guess is a 9" f/5 Gundlach Petzval-design given where I found it. But has anyone seen a similar lens with similar characteristics? Do Petzvals have greatly asymmetrical elements?
Thanks!
Steve
) and re-assembled ass backwards or worse. JG Motamedi had a couple of useful sketches that he posted once that shows the original Petzval config and the later Dallmeyer "Patent" design. Maybe he'll post those again. I've used them more than once.
