newbie question: what is a rectilinear lens and..

[kelzo]

....is there a type that is also a portrait or petzval type? My thinking has been that rectilinear lenses are crisper (or try to be) than the petzvals with that swirly bokeh. I know there is a lot of information here about both, but it's A LOT of information and my brain is already reeling from too much studying up on alt pro. A quick synopsis anyone?
Thanks,
Kel

[Jason Greenberg Motamedi]

The Petzval portrait was designed by Max Petzval and orginally made by Voigtlander in Vienna (who never paid the designer) in 1840. If used at the intended focal lengths (9" for 1/4 plate, 11" for 1/2 plate, 16" for whole plate) and for portraiture it will not create the swirlies. In center they can be remarkably sharp.

In 1866 Dallmeyer designed the RR and Steinheil designed the Aplanat; the same design but different names and different companies producing them. The RR/Aplanat was a marked improvement on the Petzval in all things but speed. While there were f4 portrait versions made, they were never as sharp as the Petzval. On the other hand the f7 versions could be very sharp accross their limited field.

The RR/Aplanat reigned supreme as a general purpose lens until the 1890s, with the advent of Zeiss's Anastigmats. The Petzval was produced in large numbers to the 1940s.

[Paul Fitzgerald]

Kel,

Petzval and meniscus were the first lenses and had a curved field, they could not reproduce a square grid as square on the film.

Rectilinear lenses were 2 meniscus lenses facing each other with the iris in the center. This corrects most problems, they could reproduce a square grid as square but they had astigmatism, vert. would be sharp but horz. would be fuzzy.

Anastigmats used the new Jena glass to correct the astigmatism.

Almost all lenses since 1890's are both rectilinear and anastigmatic and fairly well color corrected.

[Neil Purling]

A good aplanat/rectilinear is very sharp in the centre, ptobably more so than the new anastigmats like the Dagor . However the Dagor that was the next big developement was a wide field lens that acheives a better balance between centre & edge at a cost of some reduction of centre sharpness.
A rectilinear may show little astigmatism but definition into the corners isn't going to be as good. They are also have coverage that changes as you stop down due to uncorrected optical defects.
A typical maker like R&J Beck of Cornhill, London listed a f4 extra-rapid rectilinear for portrait work, but to cover 4x5 (without movements of course ) you'd need a 7.5" lens, which is 188mm.
Normal speed for one of this kind was f8. A 6" (150mm) will cover 4x5 at f8, giving some room for use of rise or fall stopped down to f22.
The last type was a f16 wide-angle rectilinear. This does 90 degrees coverage so a 150mm example makes a cheap wide-angle for 10x8.
I have a rectilinear lens off a Kodak Autographic folder. This lens was never meant to do any better than approx the quarter plate format. The Autographic used a 116 film with a image 4"x2.25". The edges are rapidly turning to mush on 4x5, but who cares. I had a retaining ring made and I thought why not have a play anyway?
I have a 150mm f5.8 Beck Biplanat and a Wray f16 W.A.R., also of 150mm focus. I have not shot any images with either of these two.
Shooting with one of these lenses and some Maco copy film re-rated to 3ASA to give a good negative in Rodinal gives you a feel for the struggles the early photographers must have had with slow materials and poor lenses.
The f4 portrait rectilinear would have had better corrections than a Petzval, even when used wide-open.

[Gordon Moat]

http://dioptrique.info/sommaire/sommaire.htm

Okay, so it is all in French, though this is a nice resource. Click on the link on the right that states "Nombre de lentilles", then click on IV to see some lenses with four elements. There are small diagrams of the optics too.

If you want sharp, then I think using a fairly modern lens is a good idea. The reason I see for using something old, like a Petzval type lens, is because you want the flaws in the images. Many people are use to seeing technically perfect shots, or shots with lots of DoF. Fewer people see short DoF, selective focus, or shots with what some would consider flaws. Yes, a Petzval design is not very optimal as lens designs go, but the look it renders is unique.

Ciao!

Gordon Moat
A G Studio (http://www.allgstudio.com)

[Ole Tjugen]

"Rectilinear" simply means that it reproduces straight lines as straight lines, there's no big mystery to that.

The simple way to accomplish this is with a symmetrical lens. Using two meniscus lenses gives a rectilinear lens, but it has to be stopped way down to give a usable sharpness and coverage. The "Rapid Rectilinear", as the name indicates, could be used at a larger aperture without losing (too much) sharpness.

A Petzval lens is very close to rectilinear in the central 10 degrees, which is where it's sharp. Great for portrait photographers who could make a portrait in a single exposure without a tea-break, but not so useful for architecture and most landscapes. So for that use, a "Landscape lens" (single meniscus or achromatic pair behind the aperture) or "Periskop" (symmetric meniscus lenses) were used. The Rapid Rectilinear was the first lens that could be used for both portraits and architecture, Steinhel called some of his versions "Universal-Aplanat".

RR's (or Aplanats, same thing) were in production until well after 1920, and some projection lenses made today are Petzval derivatives.

The invention of the Zeiss Anastigmats did NOT mean the end of the RR; Zeiss had a virtual monopoly until 1905 with all that meant in terms of price. The Dagor was NOT "the next big development", but one anastigmat among many. But being the first 3+3 anastigmat it forced other manufacturers to use rather inventive tricks to avoid the patent...

Changes in coverage as you stop down is not limited to rectilinears, you will find that with all but a very few special lenses.

[fix_se]

Another newbie question. How do you determine if an old unnamed brass lens is a petzval. I have an old one with four lenses. Two cemented in the front and two with (rather much) space between in the back. Is all lenses with such a combination petzvals?

[Ole Tjugen]

Not all of them, but quite a lot of them are.

If it's unnamed, Petzval is more likely - and if named we can (usually) find out.

[fix_se]

Thanks, is there anyway that one can find out if a unnamed lens is a petzval or not. Somewhere I read about study some kind of reflections but I couldn't figure out how to do.

[Ole Tjugen]

Most of the "reflection studies" only go as far as determining the number of lenses in each cell, and wherther or not they're cemented.

Using reflections to determine the curvature of each surface is a little more tricky, but can be really useful to tell the difference between a Rapid Rectilinear and an older "Symmetrical", or between a Dagor and a "reverse Dagor". Going beyond that again gets really tricky. :)

[fix_se]

Thanks for the info. Is there any other way to determine if I have a petzval or should I be satisfied with having a "perhaps-a-petzval" ;)

Right now I am up to making a lensboard from a piece of wood for trying it next week.
I am going to try the gallo-shutter, which I have read about, but is also thinking about using som ND-filters (grey). Does anyone use these for getting slower speeds with old brass lenses without shutters?

[Gordon Moat]

There are also lenses for old magic lantern projectors. In my recent research it seemed that there were many of Petzval type construction. Quite often these would not have name nor indication of maker on them.

Take a look at the link I posted earlier to that French website. Click on one of the diagrams, then see how the two rear air spaced elements are placed in the barrel. If the shape (curvature) and placement are Petzval type, then the construction is likely Petzval type.

http://dioptrique.info/base/i/i_petzval.htm

Then you might want to test coverage of the lens. I checked my HB&H lens by rubber banding it onto my 4x5, then running a quick Polaroid. An informal test was enough to confirm to me that this was a lens I wanted to use. Now all I have to do is adapt the mounting flange to a Technika lensboard.

Ciao!

Gordon Moat
A G Studio (http://www.allgstudio.com)

[kelzo]

Wow, I take off for a day and a half, and look at all of the great replies I come back to!
So, both petzvals and rectilinears can lose considerable sharpness toward the edges when wide open, but the rectilinears don't have the swirly bokeh. Oversimplified, but I think that's what I was wondering about most here.
Thanks all!!

[Glenn Thoreson]

Regarding ND filters, that's the easiest way to get speeds slow enough for a lens cap shutter. Have fun with your old lens. They have a unique way of looking at things.