Fluo equivalence

rawfa

rawfa

Veteran
Hi,

I've been looking into some daylight kits and I saw one that carried 4 30w fluorescent ligth bulbs. I have read somewhere that a 30w fluorescent light is equivalent to about 150w regular. Is this right? Because in this case a set of 4 30w fluo light bulbs (total of 120w) would be equivalent to 600w, which is actually good.
 
you cant really compare as its apples and oranges - Watt for watt Floros do put out more light - but its a different quality - very soft and falls off very quickly. Tungsten (I think what you mean by tungsten) has a longer throw and is much harder - but if you are tlaking about daylight then you need to gel your tungsten with CTB - full CTB cuts output by 75%
 
Its more like about 3 to 4 times not 5 times. So the 120w kit would really be more like 480w and that all depends upon the efficiency of the ballasts in the base of the bulbs which tend to be not as great as separate ballast solutions. I usually recommend the self-ballasted bulbs for those doing DIY fluorescent fixtures for video/film as its easier to put together. Fluorescent is more efficient than tungsten because its simply more efficient at converting from energy to light without heat than tungsten is. As the previous poster observed though its always a soft light and can't be made to be hard whereas tungsten is hard and can be made soft if necessary. HMI/metal halide is the energy efficient alternative for hard point lighting.
 
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In a basic 3 point lighting setup you need a key light, a back light, and a fill light or bounce card. The key and fill should usually be soft but the back should be pretty hard. Its easy to make a hard light soft but impossible to make a soft light truely hard, so hard lights are more flexible.

Another important factor is Color Rendering Index. I just got a set of four 42w BlueMax CFLs which have a CRI above 90 and a 5900K temp. Now I am in the process of making softlight fixtures to try to get the most out of them. The quality of the light they put out is amazing, and I will probably buy a bunch of them to use in practical fixtures to flood a retail location I plan on shooting in. The more expensive backlight is used to edge out an actor from the background, so its CRI isn't quite as important as the key and fill, but you may want to use that fixture in another creative way so don't totally discount its CRI.

Soft light by its nature does scatter, so properly controlling it is a must. Unfortunately, controlling it can mean clipping out the light you don't want which lowers its output. For example, adding a black grid to the front of the fixture will harden the light a bit by absorbing the light that is not going directly from the bulb's surface to the target surface. The shadows behind the object do harden a little, buy you may have lost 1/2 stop or more in the process. The tighter your grid weave the harder the light, but at the expense of light loss.

A good starting point would be two soft lights and at least one hard light. I'm planning on putting together a set of BlueMax softs and coollights HMI fresnels. It will be a challenge to properly design and create the softlight fixtures, but I am very good at (and actually enjoy) fabrication and I'll probably be posting some of my designs soon.

Bob
 
Thanks guys. This helps a lot. I have another question though. Wouldn't it be hard to mix fluo and tungsten, taking in consideration the different color dominances? I simply love to light with fluo light and I kind of fail to see where would a tungsten have better results. I'm sorry for my ignorance. I'm not a DP, I'm just a director that wants now to have it's own lightning equipment for more personal projects.
 
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