LF Portrait Bokeh Okeh Dokeh! 15" Bausch & Lomb Projection Petzval f4.5

[jimgalli]

Jim,
I'm sick and tired seeing these great shots from your bargain finds. Please post some pix of images from lenses that you used your mortage money for.

OK, comin right up I just spent my wifes christmas present money for a Pinkham & Smith Visual Quality 13". Can't wait to see what that EXPENSIVE bad boy will do. Must be something to the legends! Hope it can keep me warm at night as I'll likely have to sleep with it.

 

[Ole]

All right, I got me a Petzval at last. A cheap one. Brass barrel corroded and dull, but should shine up nicely if I should want it to sparkle. Glass dirty, but that too should clean up nicely.

But: The negative element in the rear group is missing... I'll be reading optical formulas until I find out what I need, then see if the local optician can help.

 

[medform-norm]

All right, I got me a Petzval at last. A cheap one. Brass barrel corroded and dull, but should shine up nicely if I should want it to sparkle. Glass dirty, but that too should clean up nicely.

But: The negative element in the rear group is missing... I'll be reading optical formulas until I find out what I need, then see if the local optician can help.

Ole,
have you found the formula yet? In our reference books the rear elements of a Petzval are normally cemented together. Odd that one is missing. Any idea why? Does the remaining element show traces of glass cement? Are you sure the remaining element is the original one?
Wow, this seems like a challenging expedition! Seeing that the Petzval is a mathematically constructed lens, chances are you will find the formula somewhere one day. It better be sooner than later, though. I hope Santa is going to bring you some help for this when Xmas comes...

Best, Norm

 

[Ole]

Oh, I have the formula somewhere. Probably in the lens library that came with OSLO. And at least half a dozen other places...

The basic Petzval construction has two cemented elements in front, and two separate ones in the rear. The inner one of these is negative. The focal lengths of the two groups are approximately the same.

In my lens, the rear has only a single positive element, with a focal length much shorter than the front group. The mounting for the rear group also has a place for one thick-edged element, further indicating that there's something missing there. As is, the focal point of the whole lens is only a few centimeters off the back of the lens. From the 7cm diameter of the front element, assuming f:3.5 should give a focal length of around 250mm...

 

[jimgalli]

Oh, I have the formula somewhere. Probably in the lens library that came with OSLO. And at least half a dozen other places...

The basic Petzval construction has two cemented elements in front, and two separate ones in the rear. The inner one of these is negative. The focal lengths of the two groups are approximately the same.

In my lens, the rear has only a single positive element, with a focal length much shorter than the front group. The mounting for the rear group also has a place for one thick-edged element, further indicating that there's something missing there. As is, the focal point of the whole lens is only a few centimeters off the back of the lens. From the 7cm diameter of the front element, assuming f:3.5 should give a focal length of around 250mm...

Ole, Any other info about your lens? Manufacturer? Does it have an aperture? Waterhouse slot? No aperture or slot would indicate a projection lens and those were usually f6.7 or so. That would make it much longer focal at 7cm.

 

[Ole]

The lens in question is still visible here.

 

[JosBurke]

Jim, As usual you have the ability to likely pull a fine image from a soda pop bottle used as a lens.You must have gobbled up all the well priced Vintage Petzval glass on that big auction site and left the overpriced scraps for me to peruse over--Great Work , Jim!
Josburke