Petzval lens orientation....

[DanK]

Would someone mind pointing me in the right direction....

I know I've seen a few posts on this in the past, but am having a heck of a time finding them again....

Two questions to answer...

Proper orientation of rear element - which direction does the 'most' convex side face? both sides are convex, one more than the other...

And, somewhere I read flipping one of the elements increases bokeh....which element is typically flipped? rear element, or center element....

Thanks,
Dan

[Ramiro Elena]

I keep this gif in my HD Garrett (Goamules) was kind to share when I had the same doubt.

[CCHarrison]

See my Petzval Lens Page for more help if needed.

Dan

[DanK]

See my Petzval Lens Page for more help if needed.

Dan

Thanks Dan,

I didn't realize that was your site....I've spent alot of time on there

Very Informative...

The Petzval Page made me question the orientation....

The first image in the J. Petzval design of 1840....shows the crown similar to the post above....more convex side facing the front

But the next image below (Nugent) looks to be opposite of above - the more convex side facing rear....

Thanks,
Dan

[CCHarrison]

According to all the texts, the original Petzval lens had a bi-convex crown glass rear element.

The "most" convex side is the interior side, if there is a "most" side. See
http://www.flickr.com/photos/43198376@N04/3976933329/ and Nugent drawing and attached


Other illustrations show the rear most Crown element as almost being Plano-convex, but again the most convex side is on the interior.

See
http://upload.wikimedia.org/wikipedi...t_lens.svg.png


Dan

[goamules]

If the rear is misconfigured you'll get more aberrations. I'm not sure if that can be called bokeh in the traditional definition. But Charley had a good post a few days ago where he shot a petzval with several configurations. If you do the math, there are quite a few ways to assemble them. Of course, they designed the lens to be as sharp, flat and fast as possible. Swirl, falloff, and other aberrations people want today were what they were trying to eliminate.

[DanK]

Thanks All.....Appreciate the responses

Dan

[Richard Rankin]

How was the rear air space determined? I have some books on lenses but they are all still overseas or I'd look it up first...

Richard

[renes]

Thanks to Dan, I just found out what Voigtlander petzval I have (that's why I was not sure if to put it on sale). I thought it's RR becouse the rear element was in one piece of glass but it's too fast (f/3.3) for RR... and than read this on http://www.antiquecameras.net/petzvallens.html :

>The next Petzval variation was in 1878 by Voigtlander. This design basically eliminated the air space in the rear group of Petzval's original design. Removing the air space was to help improve contrast and reduce flare, over Petzval's original design, but from actual accounts, the improvements appeared minimal and the lens wasnt quite as sharp as other Petzval lenses.

Hermann Wilhelm Vogel wrote in his book, The Progress of Photography Since the Year 1879;

"Voigtlander's new Portrait Lens.—This has a front combination similar to the old Petzval. But the back combination consists of two single lenses cemented, by which the reflection of light occurring in the old form with separated lenses is avoided. The focus of these lenses is relatively shorter than that of the old form with similar opening. For instance, Voigtlander's C lens, by substituting the new back combination, has its focus shortened from 10 inches to 7 1/2 inches, thus increasing the illumination in the proportion 9:16. The new back combinations may be bought separately, so as to be used with any lenses by the same maker. We thus have the power to shorten or lengthen the focus, and correspondingly increase or lessen the light at will, by using the new form of back combination."

Voigtlander updated the Petzval design in 1878 by cementing the front and rear element groups thereby eliminating two glass-air surfaces, which should improve contrast. <

Was it patented and did others petzval makers use this design (p.e. Darlot)?

[CCHarrison]

There is a British patent on the Voigtlander 1878 design = Patent 4756/1878

Kingslake reports that this design was used later on for some small projection lenses. I dont know of any other traditional camera lens maker that used this design. By 1878 there was a lot more choices in lenses and this particular lens did not make a significant impact on the portrait lens market.


FROM the book, The progress of photography since the year 1879

"Voigtlander's new Portrait Lens.—This has a front combination similar to the old Petzval. But the back combination consists of two single lenses cemented, by which the reflection of light occurring in the old form with separated lenses is avoided. The focus of these lenses is relatively shorter than that of the old form with similar opening. For instance, Voigtlander's C lens, by substituting the new back combination, has its focus shortened from 10 inches to 7 1/2 inches, thus increasing the illumination in the proportion 9 : 16. The new back combinations may be bought separately, so as to be used with any lenses by the same maker. We thus have the power to shorten or lengthen the focus, and correspondingly increase or lessen the light at will, by using the new form of back combination"


Dan