In the Aristo the diffuser is just a piece of translucent plastic, nothing special.
I have been under the impression (wrongly?) that the cold light was more diffused than the other diffusion-type heads. I purchase one not long ago but am not set up so have not used it yet.
So to those in the know what do I need to convert my omega 4x5 enlarger to a nifty 8x10 enlarger?
Its pretty easy to test. Just projection print any left-over film control strip on to graded paper using each light source.
John Sexton demonstrated this to me once in his darkroom, using grade-5 paper. We were able to see the curved tube of his cold-light head. Not very uniform, I tell you. My dichroic head has a definite light fall-off to the edges, but thsat doesn't hurt too much (automatic edge burn).
So to those in the know what do I need to convert my omega 4x5 enlarger to a nifty 8x10 enlarger?
I completely solved this by adding a second acrylic diffusion sheet spaced 1/4-inch from the first one. However, substantial edge fall off results; one then needs a cold light head at least one inch larger in each direction than the largest negative to be enlarged.John Sexton demonstrated this to me once in his darkroom, using grade-5 paper. We were able to see the curved tube of his cold-light head. Not very uniform, I tell you...
Unfortunately, the result of light source edge fall off is automatic "edge dodge," not burn....My dichroic head has a definite light fall-off to the edges, but thsat doesn't hurt too much (automatic edge burn).
I have a 2000w dichro head for my 8x10 enlarger, yet I normally use an Aristo cold-light. The cold-light is MUCH quieter and MUCH cooler.......given the simplicity of other diffusion-type heads, why do you prefer a cold-light head, and what are the reasons to buy one in your opinion? What can they do, another diffusion head cannot?
Oh yes, I'm not surprised. But I was referring to checking for the Collier effect by projecting step wedges made of silver film (ie old control strips rather than the step wedge itself) and checking the contrast range to which they printed. There should be a small difference between condenser and diffuse ,but Aristo and dichro head would be the same. (I guess if they were not the same one could write it up in a technical journal)
The main reason for the popularity of cold light heads is that big dichroic heads used to be very expensive, heavy, moderately difficult to adapt to a non-matching enlarger, complicated, and as mentioned they throw less heat the a comparable output incandescent head. An Aristo was often about 1/10th of the cost, much lighter, simpler (less to go wrong. Easy to fix.), more efficient, and came in a wide variety of sizes. My first 8x10 enlarger was an Elwood. I bought an Aristo head for it with the V54 bulb and a metrolux timer. This setup worked very well. Given that the cost of big color heads has nose dived, the cold lights aren't as compelling an alternative, although they're still very good, especially with aV54 bulb, which gives a very good range of contrast adjustment with VC filters.
I completely solved this by adding a second acrylic diffusion sheet spaced 1/4-inch from the first one. However, substantial edge fall off results; one then needs a cold light head at least one inch larger in each direction than the largest negative to be enlarged.
Unfortunately, the result of light source edge fall off is automatic "edge dodge," not burn.
Some dichroic heads, like the 4x5 LPLs John Sexton and I use, have diffusion materials that are thicker in their center than at their edges, thereby providing extremely even illumination to all parts of the negative.
I assume, your talking about the Callier effect?.
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