Coverage & behaviour of Petvals

[Neil Purling]

What would the coverage of a Petzval lens be? The only work I have suggests 40 degrees. Do they usually vignette after that?
I hope that this lens will cover most of the width of a 4x5 sheet, leaving a circular image.
The swirlies seem to affect fine detail in out of focus planes, I like that effect.

The lens is a ex-lantern lens. No name of course. No idea of the focal length. Abt 5" perhaps. I think the plates were about 4" square the lantern would have handled.
The lens was screwed into a thin ring of threaded brass, which was then apparently soldered to a spun brass peice.
After having cleaned up the optics I am hoping I can get a local engineering form to re-cut a pattern Pacemaker Graflex panel with a hole of the thread diameter using the existing hole as a pilot. Hopefully they could cut the spun bit off the old mount so I can use the threaded part as a retaining ring without recourse to S.K. Grimes for help.

[BarryS]

Depends what you mean by "coverage". If you mean illuminates with a sharp center, generous out of focus area, and massive aberrations at the edges, then Petzval lenses usually cover a little less than their focal length at infinity. If you have a 5" Petzval, it may throw a circle on 4x5 sheet of film. At the very least, you're going to get some serious vignetting at infinity.

[Jim Galli]

30 to 40 degrees. They are a long-ish tube by design. Ya gets what ya gets. Chances are if it is dark in the corners beyond your taste, try finding objects that are closer and see if you like it. Petzval's don't lend themselves to pictorial scenics at infinity anyways imho of course.

[Ole Tjugen]

The coverage is usually stated as 10 degrees, with a comment that they are hopelessly soft outside of that. But that soft part is where the "swirleys" live, so they are often used up to 40 degrees or so, whereafter the long barrrel leads to severe vignetting.

[Neil Purling]

I was planning on trying this lens out in a old graveyard or churchyard where the out of focus vegetation or tombs might help induce the swirlies.
I like historical re-enactmernts too. A Petzval would be grand where the massive aberrations would add to the period flavour of the photograph.

BTW my first Petzval was the slide projector lens I mounted into a Polaroid Copal in a vulgar fashion. The spacing is probably off. Will this inevtiably knacker the central definition?

[Gene McCluney]

A Petzval would be grand where the massive aberrations would add to the period flavour of the photograph.

If you look at many Civil War era photographs shot by professionals, you see very few that have swirlies. The swirl effect is almost a modern adoption of using the lenses beyond their intended coverage. Not that it is bad, it is cool, but it is not very authentic. The only time a professional Civil War era photographer got swirlies was when he "had" to get the photo, and couldn't back up enough to use a longer lens.

Early photographers did not set out to shoot photos with massive distortions in them, in fact the standard was very sharp. In portraits they did retouching on the plate to hide skin blemishes. For a blue-sensitive only wet-plate a lens can be "tack" sharp and yet be undercorrected when used on modern panchromatic films.

[goamules]

Gene's right, what is today a petzval's signature, was in the day it's flaws. They used larger ones than would be expected to avoid the edge abberations in the day. I just wrote an article to that effect, to be published next month.....

But what was "period" and is still a nice effect, is the curved field, which creates rapid falloff as you head out of center. They also have a short depth of field, wide open. Together this makes for an interesting portrait lens, or even some creative landscapes or larger groups of people. In the day, they'd have the people on the edges move in closer, to be more in focus...sometimes.

[Jason Greenberg Motamedi]

From what I have read, the following focal lengths for portraits were "recommended" by sales people, authors, and manufacturers during the Daguerreian era.

4/4 Plate: 16"
1/2 Plate: 11"
1/4 Plate: 9"

However, users would occasionally "push" their lenses one format larger (eg: using an 11" lens with whole plate), although this was not a preferred practice.

[Neil Purling]

Has anyone shot with just the front group of a Petzval?
I have just done two quick sheets with the front part of the Petzval I stuck into the Polaroid Copal #1.

As for my Lantern Petzval I have recovered the mounting from the lantern.
A local engineering firm is to mill off most of the spun brass part and re-cut the hole in a Graflex lens panel. I should be able to mount it up and shoot by the weekend.

[walter23]

The coverage is usually stated as 10 degrees, with a comment that they are hopelessly soft outside of that. But that soft part is where the "swirleys" live, so they are often used up to 40 degrees or so, whereafter the long barrrel leads to severe vignetting.

Yeah, I think they tend to just cut off at a certain point. I have a 5 1/2" one (dallmeyer projection lens) that vignettes on 4x5, and by vignette I do mean just total cutoff. Of course it becomes less of an issue with closer focus.