Scratch on condenser lens

[William Mortensen]

Not specific to large format, but you guys are such a great resource, I like to pick on you... One of our high school enlargers has a big scratch on the condenser lens, bad enough it shows up when the lens is stopped down about halfway. Is there any fix for this, or do we just have an enlarger for parts?

[John Kasaian]

Quick fix: replace the condensers with a cold light.

[Herbert A Terbrack]

You could try painting the scratch with black ink or non reflective paint. This may cut down the light scatter and allow you to use the lens.

[Ralph Barker]

You might try that eyeglass repair solution advertised on TV that seems to fill scratches with some sort of polymer. Or, you might see if adding some diffusion above the condenser would help. Otherwise, it may be a matter of finding a replacement part, or starting your own "spares" bin.

[Dan Jolicoeur]

What do you have for an enlarger? If you have a omega D2 I may be able to help?
Dan

[Patrik Roseen]

Turn the condensor lens 'upside down'!

The condensor lens is usually symmetric so this should probably do the trick. If it is contained in a housing you just need to unscrew it...turn them around...and screw it all together again.

[Patrik Roseen]

...I should add that as you stop the lens down the 'scratch' will be included in the DOF above/behind the negative. By turning it upside down the scratch will be out of the DOF. The scratch on top of the condensor lens does not impact too much unless it is very bad. I have positive experience from doing this myself...it works until you have a new scratch...

[ronald moravec]

First try putting on top. Second rotate so it is either close or far rather than left or right as it may be out of the image area.

Polish it out with very fine polishing compound. You start with a course grit to get the scratch out and then to finer ones so the dullness polishes away. Polish crosswise just the scratch area and remove as little as possible.

Lastly add a piece of tracing paper or diffusion material above the top condenser. This will soften the enlarger one half grade and reduce the light some.

[William Mortensen]

Can't do a cold light; we use variable contrast papers.

Can't paint it black, it would show up even more. That trick works on taking lenses/enlarger lenses, but on condensers it's positioned to close to the negative and shows up in the image.

The scratch is in the center of the crown where the two crowns come together. rotating or swiching the lenses won't move it significantly.

Polishing the lenses may do the trick. You guys are great!

[Richard Schlesinger]

How about just removing the offending (ed) condenser altogether? As I remember Leitz/Leica always had a single condenser in their enlargers and it seemed to work fine? Wouldn't cost a thing. Probably put the good condenser flat side down next to the film.

[William Mortensen]

Grump- this will be tried, hopefully tomorrow. The big question is whether the illumination stays even. I'll try them with no condenser at all too, though this will lower the contrast to diffusion level, I presume.

Dan- it's on a Bessler 23C. I've also got one on a Durst 6x7. My D2 and D2V are fine... for now, (gol-durn high school kids! Gotta love 'em, though.) Thanks for the offer!

Hermit- thanks for your offer also, but I think I know where I can get some for free locally.

As always, a great resource here!

[Donald Qualls]

FWIW, I have a Zone VI cold light and use VC paper by preference. Works fine, though I only split filter, and don't attempt to hit a specific grade and then transfer that information to another enlarger...

[William Mortensen]

Odd, I had a Besseler 57MB (5x7) with a Cold head light source. Filters had almost no effect on the contrast of VC papers. I think the light was fairly blue, so it may have been too restricted a wavelength to properly expose both emulsions when filtered.

BTW, does anyone know who invented the Cold head enlarger?

[Bruce Pottorff]

Mark,
Piece o' cake. I've got several 23Cs in my classroom for parts. I can send you a cond. lens. You pay shipping.

Bruce

[Oren Grad]

Odd, I had a Besseler 57MB (5x7) with a Cold head light source. Filters had almost no effect on the contrast of VC papers. I think the light was fairly blue, so it may have been too restricted a wavelength to properly expose both emulsions when filtered.

Mark, the Aristo V54 lamp (http://www.aristogrid.com/Tech01.htm) was designed to fix that problem.