Heliar cell spacing

I came upon a set of cells (2) from a Voigtlander f4.5 18cm Heliar, but they were not in shutter or barrel, just wrapped in cloth and stuffed into a metal tin. They are in wonderfully clean shape and I'd like to test them. The original shutter seems to have been a #2 Compur (dial set) and there is some reference on line to remounting them in a #3 Compound, but it is likely to be somewhat expensive since it requires machining spacers. I have two questions for the lens gurus out there: Since the Heliar design consists of a cemented pair on either side of a biconvex center element, is it likely that I am missing something? I haven't been able to take either cell apart. Second, is there anyone who might have a reference to the spacing of these cells so that I might jury-rig a barrel mount for testing?

Thanks in advance.

Whitey, one cell should hold a cemented doublet and a singlet, the other should hold a cemented doublet. To make sure that all of the pieces of glass are there, count reflections. If all's well you'll see four strong reflections from one cell, two strong reflections from the other. Use a point source of light, multiple sources make counting harder than it needs to be.

Your best bet on spacing is probably to measure the cell's mount threads diameter. This may tell you which size shutter they fit. Then find such a shutter, screw them in, and try the lens out. With ancient lenses, if yours is ancient (if there's a serial number on either cell, what is it?), finding cell spacing isn't easy.

Thanks, Dan. I believe the thread diameter is just under 46mm, the right size for the Compur #2 but not really for anything else without some work (just a tiny bit too large for the Ilex #3) and the #2 Compur is a rare beast at best. I can't remember the last time I saw one. The thickness of that shutter is listed as 26.75 mm, so that is probably my best starting point in making a quick-and-dirty mount.

I haven't done a reflection count primarily because I seem to be quite bad at it, but I can always try again. Thanks for the tip about a single source making is easier; I am easily confused at times. I looked up the diagrams for the barrel lenses, where the center element is mounted all by itself, not in a cell, and assumed the spacing of that element would make adding it to either the front (more likely?) or the rear would be a problem, but you know what they say about assumptions. I haven't got the lens with me at the moment, but I'll check the serial number. It is not ancient, just old. I believe it was mounted in a shutter at one time.

This is the Heliar diagram shown in the lens collectors vade mecum. The lines at the red arrows are the aperture blades. One cell should be larger than the other and the end curvature of the elements distinctively different on the larger cell.

If you have one cell on fine threads then looking at the ariel image of a bright star like Sirus near to axis as you screw it in or out for minium spread to locate the best image, you will need magnification to pick the best point.

Antiques were sometimes marked for best position like that and floating element lenses moved for object distance use same technique (your lens would be set for landscapes if you use Sirus).

shutterfinger said:

This is the Heliar diagram shown in the lens collectors vade mecum. The lines at the red arrows are the aperture blades. One cell should be larger than the other and the end curvature of the elements distinctively different on the larger cell.

Click to expand...

Charles, the Heliar (also think Dynar) was redesigned many times. Some versions put the diaphragm in front of (closer to the subject than) the central singlet, others put it behind (closer to the film than) the central singlet. Curvatures etc. of the cemented doublets also changed.

On this point, see www.dioptrique.info

Dan Fromm said:

Charles, the Heliar (also think Dynar) was redesigned many times. Some versions put the diaphragm in front of (closer to the subject than) the central singlet, others put it behind (closer to the film than) the central singlet. Curvatures etc. of the cemented doublets also changed.

On this point, see www.dioptrique.info

Click to expand...

The position of the iris is varied similarly in the Elmar and Tessar.

There (reportedly) is very little dependence of performance on either iris position after computer optimisation, with the modern glass catalogue of the thin lens triplets.

Xmas said:

The position of the iris is varied similarly in the Elmar and Tessar.

There (reportedly) is very little dependence of performance on either iris position after computer optimisation, with the modern glass catalogue of the thin lens triplets.

Click to expand...

Nearly all Tessars (a Zeiss trade name) and clones have the diaphragm between the second singlet and the cemented doublet. Elmar is a Leitz trade name and as tessar clones go is an outlier.

If you were talking about the effects of aperture position on a heliar type lens' performance, for perfectly symmetrical heliar types (Apo-Saphir, Apo-Skopar) reversing the lens (= moving the aperture from one side of the central singlet to the other, without changing spacing) seems to have no visible effect on image quality. But for asymmetrical lenses I think the usual rules apply: the aperture's position affects lateral color, tangential field curvature, distortion and coma.

In any case, we're talking about a relatively ancient asymmetrical lens designed when a computer was a person.

This has all been really helpful. Thanks to all of you for chiming in. I have been pretty busy the last few days, sifting through donations and consignments to the Photo Historical Society I serve, but I plan to get back to playing with this lens today.

Shutterfinger, the diagram and table you posted for the Compur 2 is new to me, but bolsters the information I have found on that particular shutter–that there were many different versions made. The dimensions I have are from the older, dial-set version, which is more likely to have been the home of the cells I have. I had seen the vade mecum diagram, but that Compur chart was not in my reference files. Thanks.