Petzval lenses

[Berndt]

It seems, that a new Petzval lens will be released:

I am curious, if somebody owns a real old one and how are the experiences, taking pictures with such a lens. What are your opinions about this lens type ? Just curious

[Stephen]

It is interesting, but the new Petzval Russian made lenses look as if they will be very expensive, as they have altered the lens coverage to suit modern smaller negative and sensor sizes.

The originals were a simple four element lens, with corrections including the exact position of the stop plate. The result on, say, an 8x10 camera, was the centre was sharp and aberration free, but as the lens still has a natural curved plane of focus, the edges were soft, with radial aberrations visible.

With the faster speeds possible, over older even simpler lenses, up to about F4 transmission stop, theoretical F3.8 approx, they revolutionised Portrait photography, where the soft edge simply does not matter that much, and was later considered desirable.

A genuine old Petzval will not work with a modern small sensor, the sweet sharp spot is larger than most sensors, so the fall off will be outside the image compared to original 1850/60/70 shots.

These Russian made Petzval lenses have a reduced field of coverage to allow the fall off to be within the size of a full frame sensor or a medium format sensor, or the equivalent in film negative terms.

I assume that the balance between sharpness and the fall off will still show, this is why the lenses are still used today. However if used with a smaller sensor, like Micro 4/3, then the effect, and the soft radical Bokeh may be lost.

The Tessar was the answer to the Petzval lens problems, gaining a flat field, but not being so good at isolating the image in the centre in the same way.

To achieve about the same effect as the Petzval with an ordinary lens, then add a very mild dioptre glass fresnel lens to about 10% of the image, with the centre missing, it will give the focus shift! Even a thick plate glass filter with a hole works about the same. also a Tessar formulae lens with a misplaced aperture ring will have the same look.

Petzval type lens remained in use for a special purpose, that of projection of a wide screen movie, where it needs lenses that have a natural curved field, at full aperture, to be able to focus on the curved projection surface. The 35 mm positive film occupies the sharp area, but the field is still curved, and can be made to match the giant wide screen of Cinemascope etc.

Stephen.

[Stephen]

Also On Micro 4/3 you can get the very same effect with C mount cine lens for a few quid!
A more positive use of a Petzval type formulae, was the amazing Garutso Balanced Cine camera lens used the early 1950's in Hollywood, which was a Petzval type, but with further glass correction elements, and a curious fine fresnel lens added to the front at the position of an extra aperture plate.

Mr Garutso built it to rival 1950's 3D, the lens focused on the back ground and the foreground at the same time, everything was in focus, but the lens only worked well with Black and White film, as the aberrations included a coloured coma flare, which showed up badly with attempts to use the lens with Technicolor. To use the lens each shot had to be set up by the cameraman very carefully, and it involved adjusting the main aperture to balance the front aperture, lots of extra work. Needless to say, the cameramen did not like them, but it was a lot less nuisance than 3d lenses!

Stephen.

[Stephen]

This is the Garutso lens Patent drawing, the extra elements are at F at the front, and at first the rear lens was four elements un-cemented, later changed to the Petzval type as the soft edge was focused by the Annular rings at the front.I think the lens maker was Baush and Lomb under contract.

I know Cooke/ Taylor Taylor Hobson tried a similar idea in the UK, for the VistaVision cameras they supplied the lens for, sold to Hollywood studios. They also found the colour fringe problem could simply not be cured.

Stephen.

[Berndt]

Stephen, the living Wikipedia. Always great to read your comments. Thanks a lot.