Originally Posted by
cardiomac
Zero to less than a quarter stop. This was the biggest challenge in designing the lamp. Many hours were spent testing various reflector/diffuser combinations until I got one that worked perfectly. One of the key discoveries was that the lens needs to be curved to work properly with the condenser lenses on the enlarger. Another technique I used is to combine diffusive and reflective surfaces within the lamp to create an even light field at the lens surface. The evenness of illumination at the easel is directly proportional to the evenness of illumination at the lens surface. Also, note that the active area of the lamp lens is only the center 3 inches, not the entire surface. This mimics the geometry of an incandescent lamp and helps reduce stray light which "softens" the print.
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