Petzval vs. Projection Petzval

[Ari]

Hi all,
I'm familiar with the kind of image a Petzval lens will make; how would the projection Petzval's images be different?
Given the same maximum aperture and same focal length, are there any significant differences in the images there two lenses make?
I know that the projection Petzval had a slightly different design, so are there also any ways to tell them apart by looking at the lenses?
Here's a B&L Petzval, a type I see often; projection or regular Petzval? Thanks

https://live.staticflickr.com/65535/49869651303_8e5a8f40bf.jpg (https://flic.kr/p/2iYNZUc)

[Greg]

This is not made to be a generalization in any way but only my experience. Over the years have owned and used a number of Petzval lenses. At one time owned a brass 1800s Petzval and a newer projection Petzval lens, both being of the same focal length. When taken apart to clean the optics, the lens spacing was definitely different. The Brass 1800s Petzval had its typical Bokeh. The projection Petzval optic had, in comparison, little Petzval Bokeh. I'm sure another member with more knowledge of optics will pipe in with a more detailed post.

[Drew Bedo]

I am not a lens guru. Many here know sdpecifics out to several decimal places . . .w3hich I respect and admire.

Here is my understanding: The projection lenses will not have a provision for drop-in stops but will usually have a focusing rack. There may be a pivoting lens cover. . The lenses made for cameras may have a slot for drop-in stops. Camera lenses may or may not have a focusing rack. Optically, I think they are the same.

[Ari]

Thanks, Drew, but I'm looking for differences in image characteristics.
Greg, sounds significant; if anyone has images to share, please post.

From Camera-Wiki: A simplified design had significant use as projection lenses for film. It had second doublet cemented and its positive component placed anterior.
Seems to indicate that the lens shown above is a projection lens.
So we know what makes its construction different; I'd like to see this in practice, if possible.

Thanks

[Two23]

My experience, based on about a dozen photo Petzvals and two projection Petzvals, is the projection ones have less coverage.


Kent in SD

[Ari]

Thanks, Kent; any difference in how they render images?

[Mark Sawyer]

Unless you've pulled it apart, I wouldn't be certain that's a Petzval. B&L made a lot of triplets that looked like that.

[Ari]

Forgot about those B&L triplets; thanks, Mark.

[goamules]

To me (I've had hundreds of Petzvals) the ones made for photography would have been made more carefully. For example, the lens grinder and polisher would have been checking the results and quality as they make a photographic lens, with the tools of the day. The projector/magic lantern lenses would not have had as much care. They would probably make those lenses for them in lots, then just assembled them from trays full of glass elements. Probably didn't even test them. A projector lens in say 1890 would cost about $5, a photograph lens from the same company about $25 to several hundred. You get what you pay for.

What would you see with a "poor quality" is more aberrations; coma, swirl, spherical, etc. Those are NOT the "petzval signature", a good lens company tried to get rid of those aberrations. But they wouldn't have messed with projector lenses.

[Ari]

Garrett, that's exactly the information I was looking for.
Many thanks for a clear, detailed explanation!

[goamules]

Not to say you might get a really good projector lens. Or you might not. You are just taking chances on how a particular one would look. I've even noticed differences in photographic petzvals by the same makers. Slight, but they can be there. You figure the projector lenses were coming out of boxes of parts, maybe even reject parts....it's not ideal for photography. Yet some people like the wacky swirl, poor sharpness, and all that....

[goamules]

Hi all,
I'm familiar with the kind of image a Petzval lens will make; how would the projection Petzval's images be different?
Given the same maximum aperture and same focal length, are there any significant differences in the images there two lenses make?
I know that the projection Petzval had a slightly different design, so are there also any ways to tell them apart by looking at the lenses?
Here's a B&L Petzval, a type I see often; projection or regular Petzval? Thanks

https://live.staticflickr.com/65535/49869651303_8e5a8f40bf.jpg (https://flic.kr/p/2iYNZUc)

There is a way to tell them apart. If the B&L has a black "band" at both ends, on the inner chrome tube, it's much more likely a Petzval. If just at the front, and the chrome tube is open at the rear, it's a Triplet. Going by memory here, but I think I remember that.

[Ari]

Great, thanks again.
Looking at the photo of the lens again, I remember reading somewhere that a recessed front element was a sure sign that it was a projection lens.
Any truth to that?

[goamules]

I'm not sure about that. Check out some of my old posts, like this (https://www.largeformatphotography.info/forum/showthread.php?130894-Trying-to-find-details-Bausch-and-Lomb-18-inch-EF&p=1328870&viewfull=1#post1328870), about telling the diff.

[goamules]

By the way, I can't see your picture in your first post. So I can't say about that one.

[Ari]

I saw that post, and it seems that the lens is more likely a Petzval. A photo you posted in that thread is nearly identical to this one.
Here's the original photo I had up.

[goamules]

I can say with 87.5% certainty it's a Petzval.

[fuegocito]

At one point I took apart a Darlot projection Petzval and a regular shooting Darlot and they look the same in terms of construction, except one has a waterhouse slot and the other didn't, and the physical size is different since it was two different focal length lens. And obviously the look on ground glass is different. I was intended to see if there is any differences between a Projection Petzval and a normal Petzval but couldn't find the proper paring between two lens of the same focal length and from the same manufacturer.

[Ari]

I can say with 87.5% certainty it's a Petzval.

Thanks, Garrett.
Yeah, that 12.5% is roughly the same as my success rate in buying a legit, true Petzval :)