Quote Originally Posted by premortho View Post
Let me say at the outset I'm certainly no expert, which is why I keep it as simple as possible. I use photofloods in hardware store reflectors. When I use ortho film I use blue bulbs. With panchro emulsions you can use either blue or white. Blue is more like sunlight, temperature wise. While I've never used a dimmer, that seems like a good idea, as the bulbs last longer, and the model is not sweltering when you turn the "heat" on. I'll have to see if I can find a dimmer that can handle the watts. One of the advantages of using photofloods is all you need is a reflective meter. I use a Weston Master ll.
Remember that as you dim an incandescent lamp the peak wavelength gets longer (ie the light gets redder) so you are probably reducing the actinic efficiency of the lamp and thus you are likely to get less actinic power for a given amount of heat - the 'actinic watts' per electrical watt* generally goes down, particularly with ortho film. It's usually better to run the lamps as hot as they are designed for, which is why the good old P1 photofloods have a colour temperature of 3400 K (tungsten Type A) and a short, but relatively efficient (for that type of incandescent) life.


*lumens per watt isn't appropriate for films that don't match the eye's spectral response - which is just about every B&W film - but it is a guide in the absence of anything else.

Best,
Helen