Quote Originally Posted by MartinP View Post
Thank you for the useful information Thomas. My wondering about the light location was for the OP in Australia! The location of the lamp in his big Durst is further away from the condensers than the usual lamp position, though it still works
Hi Martin - the bulb position could be moved as it is mounted to the same metal track to which I have mounted the LED. I'm not an expert on the physics of light dispersion although I wondered myself about this as the opening which used to hold the heat resistant glass (I removed) is much smaller than the mirror and the 5x7 inch maximum format. My test was to expose a piece of zone 5 negative at various times to check for light fall off at usual working apertures. I could not see any with 6x7cm or 4x5 inch formats. My amateur hypothesis is the LED may be more precise and uniform than a bulb as the light is coming from a broader source of LED units from a flat field as compared to the narrow filament of a bulb through a curved surface?

As Thomas also indicated, I was quite precise with the LED mounting hole on the board using a spirit level to ensure the LED was exactly aligned to the square opening in the lamp housing. You can see some of my pencil marks on the board in the photo.