opal diffusion glass

[Nick Halvas]

I have a Beseler 4x5 enlarger with a condensor head. I would like to find a source for securing a piece of opal glass (which will diffuse) the light and provide a cold head type of luminosity. I've tried many resources and can't seem to find a company or a source who would cut a piece of glass that I could place in the enlarger. Any help would be appreciated. Thanks very much in advance to all who respond.
Nick

[lee\c]

why not try buying it from Aristo. www.aristogrid.com

leec

[Oren Grad]

Here is one source for opal glass:

www.edmundoptics.com/onlinecatalog/DisplayProduct.cfm?productid=1671 (http://www.edmundoptics.com/onlinecatalog/DisplayProduct.cfm?productid=1671)

It may not be quite what you have in mind, though. I did some experiments with Edmund opal glass quite a few years ago, and found the illumination loss to be too high for practical use. Perhaps the product has changed since then.

[Andre Noble]

Nick,

I did just this about 5 years ago with my Omega D5500 4x5 enlarger. It works wonderfully. I went to a high quality glass store in Beverly Hills, and requested (If I recall) 'flashed diffuse opal' glass. They had some and were able to custom cut a 6" diameter piece (I brought the part of my Omega condenser that the piece would have to fit it, explained what I wanted) and it fits perfectly.

Some things to be aware of:

1) The opal glass goes at the very end of your condenser assembly. Beware of Newton rings with glass on glass contact with your opal glass and bottom condenseser lens. Use four 4 thin, small spacers at 90 degrees to each other on the very edges between your opal glass and condenser glass to avoid newton rings( I rolled up very tiny pieces of putty into a ball for spaces).

2) Configure any adjustable condenser lenses for the 4x5 format setting (even if you are enlarging 35mm or med format). The opal glass, because of it's opaqueness, will throw internal reflections back through the assembly and give uneven light across the smaller formats otherwise.

3) There is going to be A LOT of light loss. I replaced the 75w bulb with a 250 watt bulb, and had to jerry-rig a little computer fan to blow air into the condenser head to keep the head from getting outrageously hot. (reminds me, I still need to get a SECOND fan to help pull air out the other side.)

This effort is well worth it. A 6" piece of opal glass cut in circle should be about $30. The fan and a cheap on/off switch for same, another $10 total.

[John Kasaian]

I had a stained glass supply shop sand blast a piece of float glass. It works.

[Conrad Hoffman]

You can also get "milk" Plexiglas from anyplace that sells industrial plastics. Works fine too.

[ronald moravec]

This will get yu a diffusion machine at the expense of a LOT of light.

A decent glass shop can cut circles in glass. Give them a sample and keep a pie shaped example with surface marking tying it to the sample.

1/16 white plexiglass is sufficient. 1/8 is way too thick. Aristo uses 1/8.

Use nothing with a pattern including Rosco.

A drop ceiling light shield is cheap and easily obtained. Cover area to be cut with tape to you don`t scratch it. Mark your circle and use a hobby shop razor saw to first cut a square, then octagon, then cut the corners once more, then file to fit. The ultimate do it your self. Remove tape and install.

Condensers are best installed by holding with a loop of string, or better yet two loops at right angles. Use the opportunity to clean them.

[Mike Phifer]

I got mine afew years ago from Steven Shuart in Kane PA.

Stephen Shuart - "Large Format Specialist", PO Box 419, Kane, PA 16735-0419, Phone (814) 837-7786, Fax (814) 837-2248

Mike

[John Kasaian]

Nick,
I think theres some on eBay under the film camera, accesories, large format heading.