I have just finished an adaptation in a Durst Laborator 1000, condenser head, and changed it to a diffuser head using LEDs. I am very much surprised with the results. First, it is incredibly fast, that means, a lot of light power output compared with the former lightbulb I was using. A few seconds with lens stopped down to f/32 is enough for a 2x magnification from 4x5. Second, as it uses a micro-controller (Arduino family) to mix green and blue light in order to get contrast control, it makes very easy to use different contrast in different areas of the same print (more troublesome with filters). Attached is an image with high contrast at foreground and low contrast for sky and background. Click image for larger version.  Name: led_head_ble_fb.jpg  Views: 71  Size: 43.0 KB  ID: 169945

Details about the project can be found at https://apenasimagens.com/en/enlarger-head-using-leds/

and I also uploaded a video:


For those of you who have thought or considered LEDs, I would like to say: go for it, it is really a step change.