Test results with 120mm Petzvar Portrait Lens

First, three factors must be borne in mind:

when any lens is used at maximum aperture, any focussing error will affect the sharpness of the result, especially with hand-held shots in a non-studio environment;
the depth of field will be quite shallow with lenses of longer-than-standard focal length, which is the case with both of these lenses. The longer the focal length, the shallower the depth of field, so this is likely to be particularly obvious with the 180mm lens.
Finally, lenses normally achieve their maximum sharpness when stopped down two or three stops.

Some of these considerations are confirmed in the present results:

the image taken with the Sonnar stopped down is sharper than the image with the Sonnar at maximum aperture
however, there does not appear to be any significant difference in sharpness between the two Petzvar images. Is this due to focussing error or narrower depth of field, perhaps? Bear in mind that the Petzvar is a manual lens, so one should focus at maximum aperture and then stop down, but with images like these, even if the photographer or the subject just sways forwards or backwards, this will change the point of sharpest focus, and with the lens stopped down, this will not be obvious in the viewfinder.

We must also remember that here we are enlarging massively a tiny portion of the images. If we printed the whole of each image at this degree of enlargement, we would have pictures 1.3 metres wide and high (over 4 ft 3" in each direction), significantly larger than life size!

The Sonnar produces images that are sharper and more contrasty than the Petzvar. In fact, perhaps they are too sharp and too contrasty, revealing skin imperfections that in real life we had not even noticed. Thus, the Petzvar produces more pleasing portraits.

Of course, excessive contrast can be corrected and excessive sharpness can be reduced.

Controlling contrast

In a studio environment, the keylight and the fill light(s) will be balanced to produce the desired contrast range.
Outdoors, look for light, neutral-coloured surfaces that will reflect light into the shadow areas of the face. Snow does this well, so can light sand, as well as other surfaces. For instance, if the subject is seated at a table with a white tablecloth, this is likely to reflect light into shadow areas, if the light source is appropriately situated.

Controlling sharpness
Photographers over the years have found various ways of reducing sharpness in portrait photography.

Some put a filter on the lens and smear Vaseline on its front surface.
A less drastic solution is to take a strip of white paper, perhaps 5mm wide, and stretch it over the front of the lens, right across the middle of the lens, holding it in place with a rubber band round the lens.
One portrait photographer that I knew, who worked with a Rolleiflex, put on the taking lens a filter that he had scratched deeply with a knife, with criss-cross scatches, some of which went right across the centre of the filter. Of course, the filter on a Rolleiflex is small. Users may not wish to sacrifice an 86mm filter for the Sonnar in this way!

With all these tricks, trial and error is required, along with meticulous note-taking. Or one can just buy a lens like the Petzvar!