I have an Ilford 500H and like it very much except for the fact of shorter times on most papers than I wish for. If I remember corectly the first 500's came with two 150watt bulbs for a total of 300 watts and then it was changed to two 300 watt bulbs for a total of 600 watts - which is what I have. I was going to get a one or two stop ND filter but would prefer to try changing the bulbs to 150 watt power out instead. As this is controlled by the cpu inside the controller - would that somehow mess things up or is it an option for me? Does anyone know and any idea what kind of 150 bulb was fitted in the first run? I'm getting some times on some paper in the 4-6 second range which is nuts. I've been doing 6x7 mostly and with the medium format diffusion box. If I put the 4x5 size diffusion box, by my thinking I will not have any problems and the times should strech out a bit (or a lot?). Any advice in that regard? Thanks!