Darlot petzval question

[papageno]

What may have been an intended use of this particular lens?

Originally it did not have aperture slot. The slot was cut out just recently. I thought, that I was buying a magic lantern lens. But I can not imagine, that somebody could enjoy watching projected images of such terrible unsharpness. Even in XIX century. Actually, the lens is sharp, but only in the very small area in the center. Move the subject 1 inch on the ground glass, and you will not be able to set the focus there. Another thing is highly pronounced field curvature. Apart from unsharpness, this will also prevent from getting reasonably sharp projected image from magic lantern.

I do not think, that it was suitable for portraiture as well, unless somebody had the patience to unscrew the front element and install a diaphragm inside. People at that time were not swirl and bokeh admirers and pictorialism came much later (as far as I know).

I made only a couple of images with this lens, and always had to stop it down at least to f11. I don't want to say that I do not like that lens, it gives interesting graphic effects. My another petzval, bigger and heavier Gasc Charconnet does not swirl, but is much sharper.

One more thing, that petzval users may find interesting: when I reversed the rear element, the lens got a little bit sharper, but it refused to focus for objects farther than about 2m and edge effects changed from swirl to diagonal smudges.

[Ole Tjugen]

What format are you using it on, and what format was it intended for?
Relatively large 6.5x9cm lantern slides would have been projected with a 40cm Petzval, which doesn't give much swirl.

[Jim Galli]

Projection petzvals typically only used the center sweet spot. Your symptoms sound like someone has reversed the positive element in the rear group. They still work but they get VERY funky. 2 most curved surfaces face each other with the thin one at the very rear. I agree the aperture was added later but looks like they did a nice job. OTOH what happens if you put an aperture on either side of the nodal point?

[papageno]

Thank you for replying to my post.
I use this lens on 5x7 camera, but usually had to crop a little bit. Not because of light fall off, but total blur at the edges. Barrel diameter is about 2 and 7/8 inch, so it's not an easy fit for 4x5 camera. I do not know, for what format it was made for.
I did not bother to measure focal length, but it looks like about 9 inch or so.
It is a classic Petzval design, I checked it. Some manufacturers, like Voigtlander (if i remember correctly) had it modified.
Aperture slot is somewhere near the middle of the lens, I guess close to the nodal point. Frankly, I do not know how to change the position of aperture with regard to the nodal point.

[Jim Galli]

LOL, just looked at your picture. Do you realize people are pulling their hair out trying to get that swirly effect. I still bet your positive meniscus is in backwards. I've reversed them on purpose before just to get the lens to do that.

[papageno]

"Do you realize people are pulling their hair out trying to get that swirly effect."

That comment made me feel better. Thanks, Jim. I still value my hair quite a lot.

[Gene McCluney]

Your lens was originally used as a projection lens for an early 35mm movie projector. This would only use the very center of the field of coverage, which is very sharp. The petzval design has a huge image circle, but as you discovered only the very center is sharp. Hence, only the center was used. The reason projection lenses were of petzval design is because of high speed. Maximum amount of light on the screen, and the field of sharpness was very adequate for the 35mm frame size.

[Jim Fitzgerald]

Like Jim said, there are people pulling their hair out for this effect. Beautiful swirl in your image.Some people do not like this look. The wet plate friends of mine would love to have your lens. I happen to like the look in your image and I think you could use it to your advantage it portrait work. Different strokes... and all that.

Jim

[eddie]

like jim g said....it is broke! send it to me!

[CCHarrison]

Learn more about Petzval's (and Darlot's ) here

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


Dan