Practicals - Use a Dimmer or lower Watt bulb?

D

DDirector

Veteran
So, I was wondering... When you have practicles in a room, what do you find to be the best way to reduce the light coming from the practicle if its too bright?

Using a dimmer or replacing the bulbs with a less wattage output?
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While shooting a short in school, my teacher suggested to replace tungsten bulbs in a studio with film balanced bulbs. Not sure exactly what that was, but he said specific bulbs for film to get correct colour temperatures. Even though it was already a tungsten bulb.
These bulbs looked as if they had long necks to them and larger a bit.
So, if I have practicles such as a lamp, would have to have them replaced with proper bulbs for film?
*I once shot a shot and didn't replace on of the bulbs in the lightstand, and in the end, even though it was a tungsten bulb, it looked green in the final image. Was that my fault for not replacing the house hold bulbs with bulbs made for film?
 
Couple of thoughts to keep in mind. Most residential bulbs are being replaced with those nasty CFL's which don't dim. On the tungsten front, the GE Reveal series bulbs have a cooler temp which some find more appealing. We use those Harbor Freight router speed controls as dimmers on practicals - work great and come ready to use.
 
-Dimmer/squezzer

-Smaller bulbs

-ND

-Scrim

-Spray the lightbulb with black "Streaks n Tips" (which can be wiped off)

-Black Wrap

-Spray part of the bulb with black bbq paint. The disadvantage of this approach is it's permanent.
 
I made little rolls (bulb size) of ND and CB gels, that I just can put over them when needed.
Just cut to size, form a tube or cone (glue together with tape) that slides over the bulb - done.

Works like a charm. I wonder why nobody is selling those.

Frank
 
Well, there's really no such thing as the "correct" color temperature. When people are concerned with color temp it's generally to achieve uniformity within the scene or to achieve a certain effect. Any color temp can be white balance and rendered white to the camera's eye, so you would only swap out bulbs to make sure that all the bulbs within the scene are of the same color.

Regarding dimmer versus lower wattage, it depends. Dimmer is more versatile but it will shift the color temperature of the bulb toward the warm end. Some bulbs also cannot be dimmed.
 
Just to review, the color temperature of tungsten movie lights is 3200K. There's film balanced for that so that colors look normal under that illumination, for example, white looks white. Video cameras have presets for tungsten balanced lighting as well. Incandescent practicals run around 2700K, which is noticeably yellower in color than tungsten movie lights. If you dim them down because they are too bright they get even lower in color temperature and hence look more yellow than when burning at full brightness. But it's done all the time with dimmers.

Bulbs that burn at 3200K are called photofloods and because they typically come in 250W and 500W varieties they are almost always too bright for a practical lamp. There are 75W ones in the standard household medium base as well but they burn slightly warm in color at around 3000K. The life of bulbs burning at 3200K is short, a few hundred hours at most because they are near the melting point for the filament. No one would tolerate such short life for an ordinary household incandescent bulb.

Once in a while you are looking for a lot of light from a practical to light a scene but more commonly you are supplying movie lighting and the practicals in the shot are there for looks and motivation. In that case you usually want them fairly dim, about what you would get from a 15W or 25W bulb. The point of using neutral density gels is that the color won't shift when you cut the light output. OTOH, practicals start out at 2700K or so anyway, so they are warmer in color than tungsten movie lights to start with.

Personally, I both switch out the existing bulbs for lower wattage ones at times and at others I put dimmers, hand squeezers, in line and cut the output that way. It's sorta random but some DPs, and maybe your teacher, hate the look of mixed color temperatures so for them I swap out the bulbs or use ND gels to minimize the difference between the movie lighting and the practicals, although it is still very obvious.

The green you encountered wouldn't have come from an incandescent, but it might have come from a compact fluorescent.

How many electrics does it take to change a light bulb? They aren't bulbs, they're globes!
 
Ah, Thanks :)

And that greenish look seens to be an ongoing thing. Not just from my practicals, but there's always a green tint to my film. No idea why. The first time I saw it I thought it was the light. But its just doing it over and over.. And there are no fluorescents being used or around
 
The electronic dimmers can create noise by making a tungsten filament vibrate which can be picked up by microphones, FYI.

I prefer lower wattage practicals rather than dimmers in part because when you dim, the color temp. drops.
 
Listen to Chris. Those are the two most common worries when using a variac to reduce voltage on a lamp. I once used a SPL meter to determin which dimmer to go with when redoing a 840+ dimmer per circuit studio.
 
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