A while ago, I hastily bought a Vivitar VI 6x7 conversion unit on eBay, in the hope of printing the occasional 6x7 negative in my collection. I buy "as is" obviously, and that time, it bit me back.
When the unit arrived, I gave it a cursory look and stowed it away for a couple of weeks. Eventually, once I put it in the enlarger, I noticed that the condenser unit only had one lens. I thought nothing of it, until I realized that the light was not properly dispersed. I remembered condenser enlarger schemas: they always have two identical positive lenses placed convex-to-convex.
The seller did his best to try to locate the missing lens, and after quite a few checks, nothing was found.
I'm left with the following dilemma: either cry a little bit over the lost money, and save to find another 6x7 conversion unit; or try to find a way to add the missing condenser lens.
Is there any hope? Are condenser lenses more or less standard between brands? Does anybody have a spare?
I called Thorlabs, and they can indeed cut something according to spec. I was wondering how could I measure the focal length of my condenser? Infinity focus test?
Can you not just give them the dimensions? It's a slice of a sphere, the diameter and the height should be all they need!
Barry, here's a schematics of the lens.
http://dl.dropbox.com/u/8959/VivitarVI-6x7-condenser - copie.pdf
I estimated focal length by focusing an infinity object and measuring the distance between the planar surface and the projected image.
Barry, is your lens of the same shape? Can you try to measure the condenser's focal length like I did and see if it roughly fits?
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