Are there any reasons to not use a dimmer vs. adjusting the distance of the lights or adjusting scrims, diffusion etc.? The idea of getting a dimmer seems so much easier than manually adjusting the lights.
It depends on the type of lighting instruments that you are using.
Of course plain ol' dimmers (i.e., rheostats, "squeeze boxes", etc.), can't be used on flo' or HMI instruments, but they can be used on tungsten instruments.
The problem is, that tungsten blubs only maintain their color balance at full juice... as you decrease it with the dimmer, yes the intensity of the light will drop, but so does the color temperature. So as your instrument gets dimmer and dimmer, it also gets more and more yellow. If you dim just a little it might not be noticable or great enough to cause balancing problems with your other instruments... but if you dim way down there will be a very obvious color shift that you may have difficulty matching with other instruments (unless you gel those a bit warmer).
Of course, if you happen to be shooting B/W, you can dim to your heart's content.
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