Quote Originally Posted by Bob Salomon View Post
Just get a fine line permanent black marker and fill it in. Grinding it out will change the curve.
There's your answer; Bob beat me to it. It is standard practice with lens defects just to black them out. The same should apply to condenser lenses. However, I could be wrong... you may see the black just as you see the scratch in your prints. It should be easy to try, though. Use paint or something you can remove easily for the test.

Still, finding replacement condensers shouldn't be all that hard either.

And, I'm curious why you (and others) seem to need a red filter to compose. I compose the image on the back of a scrap sheet of paper in the easel using white light. I compose and focus with the lens wide open, then turn off the light, close down and insert a piece of photo paper into the easel and expose. At no time during exposure do I need to use a red filter... Maybe you're doing something more exotic that I do.

If you really do need your red filter, what's to stop you from just making one to fit into the filter holder you are using with your cold-light head? I assume you are filtering somehow and using VC paper. A piece of rubylith or the like cut to the right size would work just fine.

Best,

Doremus