Doing the testing for the report on the Lomo version of the 1840 Petzval lens was fun. It involved carefully un-boxing and photographing it for the shop weblog, and then testing it out for this column. The model and her husband came over and we had caviar on crackers, beer, and jam doughnuts. No calories were counted and all went well.
The lens, though, is somewhat of a problem. Oh, it is a fine product, and does exactly what it promises to do – and will probably continue to do it for another 150 years…but the designers have been put into a bit of a spot.
You see the original Petzval lenses were used with much bigger sensors than a modern camera can afford. The sensors were silvered copper plates or glass plates coated with sticky colloidion and then dipped into chemicals. As pictures in those days were destined to be the size that they were when taken, they took them on large pieces of copper or glass. We’re stuck with either 18mm x 24mm or 24mm x 36mm electronic sensors.
As a result, the focal lengths that the new Petzvals are made in are 85mm or 58mm. These can certainly focus to about 1 metre, and they do give some of the swirly bokeh that the originals were noted for, but the fact that the originals projected onto a larger image catcher meant that they had longer focal lengths…hence shallower depth of field…hence more swirly effect.
The aberrations that were displeasing then are sought after now, but the short lengths clean these up a lot. The old photogs would have been pleased, but the new people really want the distorted old look. It’s geometry, folks, and isn’t amenable to fancy footwork.
Were I to imagine how it might be done, I would make a longer Petz, put it in front of a roll-film camera back – and here the Lomo people have a couple of cheap candidates – and make do with a one-speed spring shutter – one speed and bulb. You could get a decent historical 6 x 9 negative from their cheap backs and by that point the swirly would be big and bold.
Still – I’m glad I got to play with it – it satisfied my curiosity for free and the caviar and jam doughnuts were great! Not on the same plate, I hasten to add.