Diffusion vs Condenser (part II)greenspun.com : LUSENET : Large format photography : One Thread
A week ago I posted a message asking if I could convert my D2 to a diffusion enlarger by adding a piece of diffusion material. I recieved a number of replies and suggestions to follow other threads for which I thank everyone for their valuable time and input.
After being pointed in the right direction I did a little experiment and removed the condensers and added a simple piece of thin, translucent plastic. The printing times were increased dramatically but so was the initial result: a far better rendition (IMHO) of my print! Very cool! So herein lie the question(s). The threads I followed say there is a difference between cold light and straight diffusion, but I cannot seem to find any further explanation. Is it simply even better tonal scale, etc.? I think the home made diffusion route is not for me and if I were to pursue a cold light modification are there any other 'pitfalls' I need to be wary of? Voltage stablizers - necessary for cold light? (I don't seem to need one for the hot light in the condenser). I have also read about a solid state booster & switching unit (on the Aristo web site)that seems to say you need one of these for solid state timers - fact or fiction?
Thanks and have a great weekend!
-- Matthew Hoag (firstname.lastname@example.org), March 30, 2001
In terms of printed tones on the paper, there is very little difference between diffused cold-light sources and diffused tunsten light sources, as long as both are really diffused. The problems with home-made diffuser are two fold: To get complete diffusion with any sort of collimated or directly illuminating tunsten light source, you may need two diffusers stacked a short distance apart (at least 1/2 inch) (similar to the double diffusion in a soft-box). Secondly, in the Beseler enlargers (I don't know about the Omegas) the diffusers are thinner at the edges and thicker at the centre to even out the falloff before it is transmitted through the lens. In other words, a simple, consistent thin piece of diffusing material may not produce truly diffuse light or sufficiently even light on the easel. Not necessarily as simple as it looks. But the only way to find out is to test your home made diffuser by printing a briefly exposed image without a negative in the carrier.
-- David Kaufman (email@example.com), March 30, 2001.
Matthew, There is also a half-way solution to minimize light loss and still get some diffusion: use both, diffuser and condenser. Test and choose position one up or the other. Things work fine, light distribution is OK and when you need some extra contrast, just slip out the diffuser. Give it a chance and maybe it works for you. Good luck.
-- Cesar Barreto (firstname.lastname@example.org), March 30, 2001.
I have a D2V that I converted to a diffusion enlarger with a piece of opal glass 25 years ago. I took the condensers out, placed the piece of opal glass at the bottom of the condenser housing and then put the condensers back into place.
I think you need the condensers in-place to even out the light. Also, if you paint the inside of the bulb housing with flat white paint, you will help even out the light source.
I have also used an Aristo cold light head and currently have a colorhead on the enlarger that I use for black and white and color. The difference between all of them?
The opal glass setup printed a little over 1 grade lower in contrast than the straight condenser setup.
The Aristo printed about 1/4 grade lower in contrast than the opal glass setup.
The colorhead prints at the same contrast level as the Aristo and gives me the ability to do split exposures (blue / green).
You may want to go to the next size larger wattage enlarger bulb with the diffusion material & condensers. Thats what I did and didn't really have heat problems as the bulb is separated from the negative by all that condenser glass (as you know). If you were doing production printing this could be an issue, but if you are making prints for yourself, the lamp housing cools by the time you've processed the print and are ready to make the next exposure.
-- steve (email@example.com), April 04, 2001.