Lantern Petzval question

[Neil Purling]

It looks to me the arrangement of a Petzval is a cemented pair at the front and a spaced pair at the rear.
If that is so, what (optically) would the front part be called?
I have not been looking into the lens, I just looked up 'Petzval' on the Net.

I know that you get the swirlies in the centre area and a smeared area outside that.
How would this change if I used the front cell only?

[Emil Schildt]

http://www.antiquecameras.net/petzvallens.html

the front lens could be called a landscape meniscus type lens - if used alone you'll not get swirl, but it can be use as a soft focus lens of sort (if used wide open)

[Mark Sawyer]

I suppose you could call the front part "the front part" or "the front cell", but most lens geeks would probably call it the achromatic cell, as that's its particular role. You actually get the swirlies in the outer area. If you use the front cell only, you'll have an English Landscape Lens with lots of spherical aberration and curved field unless you stop it well down. This was a fairly common practice in the early years of photography.

[seezee]

Not sure if this answers your questions (http://cargocollective.com/mauritsbollen/Petzval-Lens-Swirl), but I think you'll find it informative. You should also look at this video (http://collodion-art.blogspot.nl/2014/11/how-does-petzval-lens-looks-like.html) by Alex Timmermans, which the article author mentions.

AFAIK, there is no name for the front element. It's just the front element, as in any lens. It is called a doublet because it consist of 2 pieces of glass, but so is the rear.

The Wikipedia article on Joseph Petzval has a pretty extensive section (https://en.wikipedia.org/wiki/Joseph_Petzval#Optics) on the lens (the lens article on Wikipedia is just a stub).

[Neil Purling]

seezee; The blog article on Petzval's by in the first link has a very dramatic shot at the top of a branch. It is exactly the way my Petzval behaves.
Unless you have enormously deep pockets I guess that raping a derelict magic lantern of it's lens is the easiest & cheapest way of getting one of these lenses.
I wonder if switching the order of the rear elements was a way of tailoring the lens to a role as a projector optic rather than one to be used on a camera.

[Neil Purling]

Update: I took my lantern lens out of the cupboard and extracted the rear component parts of the rear group. It was a screw-in ring, a spacer that slid in and the elements themselves. The rear flint component was the proper way around, the crown glass was reversed. This would be example #8 if you read the article on Petzval swirl. I re-assembled the group according to the proper arrangement in Joseph Petzva's original formula. The correct example is diagram #1 in the Petzval swirl article. I used the spacer ring to separate the two rear glass elements.
The images taken with the Ed Liesgang Petzval show some distortion of straight lines in the incorrect arrangement, which I could see through the rear group. This is absent in the reassembled rear group. I will do a film test to confirm things are OK.

[Steven Tribe]

Dear Neil.

Historically, the Petzval front lens (achromat) is developed from the pre-photography era design of the large front lens of telscopes and other optical instruments (called objectives). So the the difference in French and UK early Petzvals is a carry-on from earlier optical traditions.

So another source of achromats is to get hold of decrepit early telescope - of which there are quite a lot around. The "Day and Night" engraved versions have an achromat about 2" across and are very suitable for photographic use. Unfortunately, this is the part which is most often U/S on half destroyed telescopes - but they can still be found, even if the selection available on xbay is diminishing year by year. Note that early telescope objectives can have non-balsam cemented pairs. They can be joined byp oil or have a tiny air space with thin tin strips holding them apart.

These single meniscus lenses, using the same design as the front lens of the Petzval, have been available since the 1840s.
Makers in the 1850's and afterwards, even designed convertible Petzval where the brasswork enable double use of their lenses. Note that the landscape menicus use requires the lens to be turned contrary to their position on a Petzval.

As regards the sequence of two lenses in the rear - no good things happen when they are reversed. These are quite commonly reversed due to incorrect assembly after cleaning and resuæt in poor performance. Reversed order did appear after Dallmeyer's patent around 1865. But this involved complete redesign of both lenses.

I have alway thought, without giving it too much optical analysis, that Projection lens should have a reversed lens design. That is, the achromat should be nearest the light/image source! In fact I have had a single projection Petzval that did have this design. This wasn't a matter of faulty assembly as the two lens cells were of different design (Thread sizes).

OK, you have done the right thing whilst I was writing this! It is easy to switch or turn the rear lenses.
Although Liesegang is now known as a projection optic specialist, they used to make ground breaking Petzvals and the convertible type I mentioned above!

[Neil Purling]

As the lens I had bought was from a projector it has no markings as to focal length or aperture. I had no idea if it would cover 4x5, but I expected not. What did surprise me was the rampant amount of positive coma present.
I have not seen what a proper portrait Petzval lens appropriate to 4x5 or half-plate would do. I assumed the awful flaws were purely because the lens was severely undersized & best used with my 6x7 roll-backs.
What focal length of Petzval was used on 4x5 or half-plate for portraits? I would have thought around 10 inches or longer.

[Steven Tribe]

No, it is less than 10". 12" is usually for full plate size. There is a recent thread which covers petzval coverage quite well.

[seezee]

What focal length of Petzval was used on 4x5 or half-plate for portraits? I would have thought around 10 inches or longer.
I've used a 105mm, which is OK if the subject is sufficiently far from the camera, but shows too much distortion for head shots, and a 250mm, which is fine for either. The former lens did not give complete coverage, which I discovered too late after developing portraits employing the maximum front rise on my Wista.

YMMV.

[Neil Purling]

The only guide I have suggests 20 degrees for a Petzval. Whether that figure means the central area of the image or the total circle of illumination I do not know.
The book is by Conrad Beck C1903. The Petzval is mentioned as it is an important optic but for portraiture the aplanat was now in favour. One would suppose that'd be used wide-open in place of the Petzval or stopped down if you were asked to make images of two or more people.

I need to go and shoot a statue with my Petzval and my aplanat & see what improvement has resulted from putting the rear elelements in right has brought.

[Neil Purling]

I have taken the Petzval out and it definitely does NOT illuminate the corners or ends of the 4x5 frame when focused at infinity.
It seems better used close-up. The vignette is not so hard, but it still does not fill the corners.
For portraiture a Petzval of a focal length three times that of the longest side of the negative was advocated. But that must be to fill most of the frame from the sharpest central area
I wonder about the diameter of the front group of a 15" Petzval..... And it's weight!

[seezee]

I have taken the Petzval out and it definitely does NOT illuminate the corners or ends of the 4x5 frame when focused at infinity.
It seems better used close-up. The vignette is not so hard, but it still does not fill the corners.
For portraiture a Petzval of a focal length three times that of the longest side of the negative was advocated. But that must be to fill most of the frame from the sharpest central area
I wonder about the diameter of the front group of a 15" Petzval..... And it's weight!

That would be a non-starter for me. To begin with, my bellows extension is only 12″. Since I'm using a large front-mounted Packard shutter, which, combined with the ~10″ Petzval, is already testing the load-bearing limits of my front standard, I wouldn't dare mount a 15″ lens there!

[Neil Purling]

Well, apparently Jim Galli sold just such a lens and that was mounted on a 8 inch wide lens panel with not a lot of room either side.
Obviously to use such a monster lens we are talking about a tailboard camera where all the focusing is done on the rear. An 8 inch lens is about the limit on my Graflex, if it fits on a Pacemaker lens panel. My Petzval is of 5" focus, or therabouts. Not quite sure about aperture. I have been assuming approx f4.