I have been printing with the condenser head on my Durst 138S. I use Ilford multigrade filters in the filter drawer for contrast control. I like the sharpness of the grain that the condensers give, and there’s something satisfying about sliding the correct condensers into the slots, due I think to their heft and how well built the machine is. But, and there’s always a ‘but’, when I want to make use of a dodge and burn mask I can’t. This is an inherent limitation of the condenser system which essentially focuses an image of the light source (bulb) through the negative and into the center of the enlarger lens. This collimated light is what’s responsible for the perceived sharpness of the prints. But it means that adding a diffusion layer as needed by the dodge / burn / pencil masks breaks the design.
I tried various methods of diffusing the existing light, but the results were wither too dim for large prints, or too uneven. So I decided to build my own light source. I had used white LEDs to make a simple head before, which worked pretty well. It was simply a bank of high power LEDs and a constant current controller which plugged into a timer. I thought about rebuilding this to fit the Durst. But given it’s a 5×7 enlarger I can’t find contrast filters large enough to fit above the negative, and I wanted to avoid under the lens filters (partially since the current set isn’t big enough to fit under the 210mm lens I have). I also enjoyed being able to set the contrast in finer steps than 1/2 a grade when I was using an Ilford 500 head on the 4×5 Omega.
So I’ve decided to build a variable contrast head. This will use two colors of LEDs; green for the soft grades; blue for the hard grades. By varying the intensity between them I should be able to produce any grade between the two extremes.
Parts have been ordered, and I’ve been playing with the LEDs and controllers. I’ll post some updates soon.