cyberjunkie
7-Feb-2011, 00:24
I have a nice early Petzval. It's a projection lens, with no waterhouse slot, flat focusing knob, and a short barrel. Unfortunately the front element is missing, but the two air-spaced glasses at the back are in perfect shape.
When i say that the barrel is short, i mean that the back cell is not fitted in a conventional way, with one or two retaining rings and possibly a spacer, but is mounted in a tube, which in turn is fitted to the barrel. The tube length is more than 3cm. I guess that the front cell had, more or less, the same shape and dimensions, because the shape of the lens shade allows to mount a similar cell at the front of the lens.
The length of the proper barrel is reduced because about 6.5cm of the total length were made by the two tubes of front and back cells.
The threads at the front and at the back are of 54mm, the only difference between the cells should be the glass diameter: screwing the back cell at the front there is no room to mount the shade, because the cell is a little too large. The front cell should have 54mm thread as well, but should also sit flush to the barrel diameter. That is not strange, as i have seen some Petzvals where the front glass is a little smaller than the lens at the back.
I hope i have described the situation with sufficient detail.
I would like to fix the lens in some way, but i have not experimented with Petzval lens swapping before...
I even tought about fitting a +2 close-up lens with a 52mm thread in place of the front cell (i guess that a 54mm thread should be difficult to find). What makes me dubious is that the separation between the cells would be totally off!
I am not sure about the focal either, a 500mm cemented achromat (like a +2 close-up lens of decent quality) was my first choice, just because a 2 1/2+ would be very difficult to find, and a 3+ could be a little too short :confused:
Unfortunately i don't have a close-up lens of suitable size at home, and i'm not willing to buy anything before asking on this forum. I am sure that many of you made this kind of experiments.
I am open to any advice. What i know for sure is that i'd hate to give it up. The two back elements alone are worthless, but the only front achromat i have at home is much smaller: no use for this Petzval, but i'd like to try to make a landscape lens fitting the cell at the back of an empty small barrel, with rotating diaphragm, i found time ago on the bay.
I end my post with a small appeal: if you have in some drawer an unused Petzval front cell with 54mm thread, and you have no use for it, i would be more than happy to pay for it, if the price is reasonable
have fun
CJ
When i say that the barrel is short, i mean that the back cell is not fitted in a conventional way, with one or two retaining rings and possibly a spacer, but is mounted in a tube, which in turn is fitted to the barrel. The tube length is more than 3cm. I guess that the front cell had, more or less, the same shape and dimensions, because the shape of the lens shade allows to mount a similar cell at the front of the lens.
The length of the proper barrel is reduced because about 6.5cm of the total length were made by the two tubes of front and back cells.
The threads at the front and at the back are of 54mm, the only difference between the cells should be the glass diameter: screwing the back cell at the front there is no room to mount the shade, because the cell is a little too large. The front cell should have 54mm thread as well, but should also sit flush to the barrel diameter. That is not strange, as i have seen some Petzvals where the front glass is a little smaller than the lens at the back.
I hope i have described the situation with sufficient detail.
I would like to fix the lens in some way, but i have not experimented with Petzval lens swapping before...
I even tought about fitting a +2 close-up lens with a 52mm thread in place of the front cell (i guess that a 54mm thread should be difficult to find). What makes me dubious is that the separation between the cells would be totally off!
I am not sure about the focal either, a 500mm cemented achromat (like a +2 close-up lens of decent quality) was my first choice, just because a 2 1/2+ would be very difficult to find, and a 3+ could be a little too short :confused:
Unfortunately i don't have a close-up lens of suitable size at home, and i'm not willing to buy anything before asking on this forum. I am sure that many of you made this kind of experiments.
I am open to any advice. What i know for sure is that i'd hate to give it up. The two back elements alone are worthless, but the only front achromat i have at home is much smaller: no use for this Petzval, but i'd like to try to make a landscape lens fitting the cell at the back of an empty small barrel, with rotating diaphragm, i found time ago on the bay.
I end my post with a small appeal: if you have in some drawer an unused Petzval front cell with 54mm thread, and you have no use for it, i would be more than happy to pay for it, if the price is reasonable
have fun
CJ