Bausch & Lomb 18/21 barrel lens

[jtomasella]

I've tried searching to find what the focal length is to no avail. Anyone know? Serial number is in the 39000 range, so 1902 is what I get.

[karl french]

Pictures would make a world of difference in terms of identifying your lens.

[jtomasella]

Pictures would make a world of difference in terms of identifying your lens.

https://www.ebay.com/itm/Bausch-Lomb-Brass-Barrel-Type-Vintage-Large-Format-Lens-18-21/133384820030?hash=item1f0e5ad53e:g:RdMAAOSwhI9ekiJ8

[Dan Fromm]

Looks like a magic lantern lens.

[karl french]

Ah, that's likely a petzval, though some of these projection lenses are triplets. Not sure those markings are focal lengths. If the whole lens was an 18" lens, just the front would be something like a 30-32" focal length.

Best way to get a ball park idea is to point the lens at something far away and focus the image on the wall. Measuring the distance from image to the center of the barrel. Though some petzvals have a nodal point that is behind the center of the barrel.

[jtomasella]

Yeah that won't help, I was just looking for an old lens with some character to use in the upper range for my 4x5. (250-300mm). Doesn't have to be new or perfect glass.