Petzval optics order
I got a petzval off ebay and was giving it a good cleaning.
Well....I might have put it back together wrong.
I havent' made a lensboard for it yet, but I wanted to see if I got it right.
I put the cemented doublet in front and the two air spaced in the back.
The curvature for all are pointing outward.
Also the thinner of the two in the back is most outward with the thicker inside.
back ( ( )) front
is that correct?
In French, though if you click on the link to the right of each of these listings, a larger diagram style image will come up. The important part is the spacer for the air gap of the rear optics. It will function with the rear optics not in proper order, but not as well as it should.
I have a few of these types of lenses. One is a Bausch & Lomb missing the metal ring for the air gap, though originally this was a magic lantern optic. I still have the extra large element that adds onto the lens, making the magic lantern grouping complete. Another is a Gundlach design, originally intended for a Simplex 35mm motion picture projector. Oddly enough, Jim Galli has (had?) a few of the same type, and found they just cover 4x5; though I have not tried that nor mounted it into a board. Then there is the 1854 Holmes, Booth & Haydens I acquired with a bunch of other gear. The HB&H optics cleaned up nicely, and after some machining on a Linhof board it fits on my 4x5; though originally for 1/4 plate, it just covers 4x5 without movements and only slight vignetting in the corners.
Gordon Moat Photography
Thanks for the link.
So based on this one, I did it as follows
Front (( (|(
Front (( double cemented (larger lens|metal spacer (smaller lens Back
In the back the smaller lens fit snugly into the larger one (if there was no spacer), so I put them together that way. I am getting an image on the GG, so I guess it's fine?? if it was messed up, what would I see?
Just as an experiment, I tried altering the order and direction of the rear two elements. In each case, except the correct order, there was a very small central area in focus, and nothing else. When the order and direction were correct, then everything looked in focus one the ground glass, out nearly to the edges. I only have one example of an image using my HB&H:
and a closer cropped image at http://www.gordonmoat.com/swops/GM_swop_16.jpg
A little tough to see on these small images, but the Petzval design is actually very sharp and crisp, at the plane of focus that the f3.4 aperture allows. Keep in mind this is a 2 seconds exposure, so a little tougher for a person to stand still. In my opinion, it would work better with a bit more distance between the subject and camera.
My suggestion to you as a next step is to shoot a few Polaroid tests at various focus distances. If you don't have a Polaroid back, then just burn a few pieces of film. Best of luck with this.
Gordon Moat Photography