400 watt halogen light?

for just a little more you can get a 1000w http://www.amazon.co.uk/gp/aw/d/B008J1V128/ref=mp_s_a_1_2?qid=1394215480&sr=8-2 remove the glass. Your time will be dependent on distance from screen and type of emulsion being used dual cure or photopolymer. With halogen and metal halide a fan to cool the bulb is recommended as heat can cause exposure problems

Thanks a lot, that's much better! Another question, my instructions for my emulsion says use a 5000 watt lamp at 1 metre away. So do I just follow these instructions with this lamp, and multiply the exposure time by 5? Or is it more complicated?

With halogen measure your screen diagonally. Then place the light approximately 1-1.5 times that distance. As for the time that will be inaccurate to try and figure that way. The bulb they are referring to is a metal halide that put off way more usable UV then a halogen. Its best to do a step wedge test that way you will test a range of times from one exposure test to figure your optimal exposure time.