Collinear glass replacement ?

[ridax]

A friend is offering a 440mm f/6.3 Voighlaender Collinear ser.II for sale. Problem is, the lens has one of its outer biconvex glass elements missing. Looks like smashed into pieces and then uncemented and thrown away and replaced by an enlarger condenser lens by some previous owner who apparently wanted the old Collinear to look good rather then be worth for taking pictures. So the lens has only 1/2 of it usable, and I am not fond of using rear parts of double anastgmats alone at all.

Is there any chance some commercial optical shop could make exactly the same glass element for a reasonable price? (I am able to cement it into its place myself.) Thanks in advance.

[goamules]

Is there any chance some commercial optical shop could make exactly the same glass element for a reasonable price? (I am able to cement it into its place myself.) Thanks in advance.

No, unless several hundred into the thousands of dollars is reasonable. What would they used for a blueprint?

[ridax]

What would they used for a blueprint?

I guess the old patent info could be found, with the glass type specs in it. And as for the radii, the other half of the Collinear can certainly be measured accurately enough.

That said, I'm still afraid the actual manufacturing can turn out to be too expensive. Even IF the appropriate glass type is available nowadays...

Still, any advice is appreciated as I'd like to be sure I've taken every possible chance.

[goamules]

Why don't you contact some "optical shops" and ask them what they'd charge and if they could do it? Ask an engineer if he can build a new airplane that does XYZ, not a pilot. Report back to us what you find out.

[E. von Hoegh]

A friend is offering a 440mm f/6.3 Voighlaender Collinear ser.II for sale. Problem is, the lens has one of its outer biconvex glass elements missing. Looks like smashed into pieces and then uncemented and thrown away and replaced by an enlarger condenser lens by some previous owner who apparently wanted the old Collinear to look good rather then be worth for taking pictures. So the lens has only 1/2 of it usable, and I am not fond of using rear parts of double anastgmats alone at all.

Is there any chance some commercial optical shop could make exactly the same glass element for a reasonable price? (I am able to cement it into its place myself.) Thanks in advance.

What is the lens worth to you? As much as a small car? If so, go ahead with your plans of having a new element made. Otherwise, go find a Collinear in decent shape. They're out there.

Replacing one element will involve identifying the types of glass used for the remaining elements, finding a modern glass which is suitable (if it exists), grinding and polishing one element - and making the requisite tooling to do so - then reassembling the lens. The information in the patent may or may not pertain to your lens, formulae were recalculated over the years as new glasses came available.

[ridax]

Why don't you contact some "optical shops" and ask them what they'd charge and if they could do it? Ask an engineer if he can build a new airplane that does XYZ, not a pilot. Report back to us what you find out.

Oh yes I'm sure all that (as well as what E. von Hoegh says, too) is very true. I just thought somebody might have already tried going the same way.... But if I'm the first one with those crazy ideas - so be it; I'll try undertaking the research myself. Going to be a long story I guess.

Still, any advice is welcome.

[Amedeus]

What is a reasonable price ? What is your budget ?

Building a one-off custom optic is not inexpensive ... Even measuring the curvature of the remaining element is going to set you back hundreds.

Less expensive to find another lens ... Ymmv

[Jim Galli]

Do yourself a favor and walk away from it. I've never had a complete collinear I liked much, let alone a bugger'd one.

[ridax]

Do yourself a favor and walk away from it. I've never had a complete collinear I liked much, let alone a bugger'd one.

I've just finished testing a shorter (and cheaper) 180mm Collinear bought a few days ago just for these testing purposes, and now I do see your advice is really the way to go... Though sharp and really not bad at all, the Collinear is nowhere near a Dagor or a Protar bokeh-wise, and is of pretty moderate coverage. I don't think I'd like to go into much trouble to get a longer one.

BTW, meanwhile I've undertaken a bit a research, and I think the exactly same glass is not produced any more. A couple of reasonably similar types of glass are available but I'm afraid recalculating the element to the new glass specs would be a bit of insane behavior - considering all the other possible expenses to the project, too....