Petzval lens questions

[jtomasella]

I bought an unmarked lens and I have a couple questions. I figured the edges would be less sharp the further from center it got. The lens has 2 front elements and one rear. The rear has 144 written on the side. No other markings on the lens. No waterhouse slot so it's just wide open. As far as I can tell it is a 280mm at F4 from doing research on here on how to calculate it. I'm guessing that's pretty close from my sample shot. Don't mind the spots, scratches and hair, I dropped the negative. Question 1 is, how do you keep the focus on the lens itself from moving? I can grab the the lens and it moves super easy inside the brass outer sleeve. Last question, is there a way to make it more blurry/soft since that is what I had bought it for. Here is a sample picture and a picture of the lens.
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[jtomasella]

I had a cheap Petzval (USD 30) fully cleaned last week, and for that I had it disassembled completely; it turned out all the lenses where at the wrong place; the lenses were also swapped in the wrong mounting.

So first check whether you lenses are placed at the right orientation. You mention that there are 2 elements at the front. At the frontside however there should reside the cemented achromat (which looks like one lens), and at the back the meniscus (inside) and the biconvex or planoconvex (at the rear outside): see also here: https://www.largeformatphotography.info/forum/showthread.php?67247-Petzval-lens-orientation

Further you won't see much of the swirly bookeh at close distant shots.

The pencil writing 144 at the side of your (cemented) achromat might indicate its focuslength.

After looking at this site it seems the 2 elements are supposed to be in the rear and the single in front.
https://antiquecameras.net/petzvallens/oldarticle.html

[Mark Sawyer]

Question 1 is, how do you keep the focus on the lens itself from moving? I can grab the the lens and it moves super easy inside the brass outer sleeve. Last question, is there a way to make it more blurry/soft since that is what I had bought it for. Here is a sample picture and a picture of the lens.


For question 1: Many Petzvals had a felt lining inside the brass barrel that the inner barrel slid against. When that's removed, the inner barrel is loose and slides around easily. Remove the drive and the inner barrel will come out completely, and you can put a layer or two of book tape/gaffer's tape/whatever inside the brass barrel to take up the space. Play with it til you find the right thickness, then reassemble.

For question 2: Basic Petzvals are not soft-focus lenses. Dallmeyer had a modification to the design that many copied, but it wasn't really very effective compared to later soft-focus lenses. You can vary the spacing between the back elements and try reversing their order (that's how the Dallmeyer redesign worked), which might give you what you want.

Another better option would be to use the front element alone as a Landscape Lens (single element). That can give a very nice soft-focus effect at about double the focal length and half the speed.

[jtomasella]

Isn't that the same as what I wrote about the front and rear? hmm perhaps the words 'cemented achromat' is confusing for you.



Btw if you lenses moves too easy, then you should (re)place the velvet liner inside the outside sleeve; it resides at the rear where there should be a recess for it.

No you didn't confuse me, in front there are two elements. According to the article I just read, they are supposed to be in the rear.

[jtomasella]

For question 1: Many Petzvals had a felt lining inside the brass barrel that the inner barrel slid against. When that's removed, the inner barrel is loose and slides around easily. Remove the drive and the inner barrel will come out completely, and you can put a layer or two of book tape/gaffer's tape/whatever inside the brass barrel to take up the space. Play with it til you find the right thickness, then reassemble.

For question 2: Basic Petzvals are not soft-focus lenses. Dallmeyer had a modification to the design that many copied, but it wasn't really very effective compared to later soft-focus lenses. You can vary the spacing between the back elements and try reversing their order (that's how the Dallmeyer redesign worked), which might give you what you want.

Another better option would be to use the front element alone as a Landscape Lens (single element). That can give a very nice soft-focus effect at about double the focal length and half the speed.

I'll look into the felt. I have some felt with an adhesive back in my art box.

[Mark Sawyer]

I'll look into the felt. I have some felt with an adhesive back in my art box.

It may be too thick, as modern felt tends to be much thicker than the old stuff. But worth a try!

[Ron (Netherlands)]

No you didn't confuse me, in front there are two elements. According to the article I just read, they are supposed to be in the rear.

I delete my suggestions to you, since other members here may read your response as though I advised the opposite.


It may be too thick, as modern felt tends to be much thicker than the old stuff. But worth a try!

Didn't they use velvet in the old days.....

[jtomasella]

I delete my suggestions to you, since other members here may read your response as though I advised the opposite.



Didn't they use velvet in the old days.....

You put me on the right track. I reinstalled the lenes acorrdind to that article and added tape to the barrel to stiffen it up some. I'll post follow up pictures after I test the current configuration.

[jtomasella]

It may be too thick, as modern felt tends to be much thicker than the old stuff. But worth a try!

Yes, it was too thick, used tape instead.

[Two23]

Actually, a Petzval construction is two elements cemented together and there are two individual elements slightly spaced apart in the rear. It's common for those two in the rear to not be set correctly. I.e., one or both are reversed.


Kent in SD

[jtomasella]

Actually, a Petzval construction is two elements cemented together and there are two individual elements slightly spaced apart in the rear. It's common for those two in the rear to not be set correctly. I.e., one or both are reversed.


Kent in SD

The two lenses were actually in the front, this has now all been corrected and they are in proper orientation. I just have to now take another test shot.

[Steven Tribe]

This is a projection Petzval.
It may be that someone had the barrel out of the brass sleeve - by releasing the focusing drive - and then reversing the tube by mistake. The fit in the original mounting mode might be less insecure.
You can influence DOF and general sharpness by inserting card apertures in front of the front cell.