converting an average condenser enlarger to diffusion

I have several mass market type condenser enlargers (Bogen, etc) and sometimes use a cut piece of plastic 'ground glass' in the filter drawer to fully diffuse the light coming from my ph140 bulb. Where do I buy more of this material? Or are there alternatives?

I was thinking about art supply stores stocking pliable sheets of diffusion material. I have tried tracing paper but the problem is the presence of detail in the paper: when I stop down the lens to f22 the detail becomes partially in focus and slightly visible on the baseboard. I need a material that is strictly homogeneous throughout. Again, the ground glass (glass or plastic) serves this purpose.

Please state sources for either of these two materials if you know of any. Also, do you have further suggestions for what should be a very simple conversion (with the only drawback being increased exposure time)? - David Lyga

The Durst M-300 came with a piece of glass for this very purpose. My father always used it when he printed so I've always left it there. With an El-Nikkor 50mm f/2.8 lens, exposure time is not a problem.

Also, while on the topic: I will state my source for the PH140 bulbs: it is 1000bulbs.com in Texas. A few years ago I bought 24 when I heard that tungsten bulbs will no longer be sold in the US. Perhaps enlarging bulbs will be an exception but the 24 bulbs cost me only about $70 and I felt that the purchase would guarantee that I would never be wanting. Currently, I believe that the bulbs are about $3.60 each plus shipping.

As an 'aside', the diffusion conversion referred to above allows one to put a normal houshold bulb in one's enlarger (after the printing is gently scraped off with a razor blade) without a black filament showing up on the baseboard. So that is an alternative to having to get a dedicated enlarger bulb. - David Lyga

You can always make a ground glass for a permanent diffuser. Its plenty easy to make yourself.

David Lyga said:

I need a material that is strictly homogeneous throughout. Again, the ground glass (glass or plastic) serves this purpose.

Please state sources for either of these two materials if you know of any.

Click to expand...

A glass shop.

You might also consider opening up the lens to about f8. But, that's another discussion ...

Roscoe and Lee make a number of diffusion gel materials that could be used in the filter drawers. Get onto their websites and choose your type. 20x24 inch sheets are around US$6 last time I looked, available from the online photo stores or your local pro shop.

Lee (no connection with the filter maker)