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How much wattage of lights should I use?

H

harmonica44

I was thinking of getting lights bright enough so that I could shoot at a low aperture and maintain a deep depth of field. Also would like to use bright enough lights so that I don't have to up the ISO over maybe 200 if that's a good idea.

But what lights are bright enough for that? The hardware store I got lights from before go up to 500 watts and those watts are good at 400 ISO with the aperture around 4.5 maybe, but no less. Or I can up the ISO and down the aperture of course. Any type of lights that are not too costly where I can up shoot with both ISO and aperture low?
 
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I'll let the techies chime in on this, but as physics expert, the further away from your subject(s) your lights are, the more watts you need. It is also possible to blowout the whites of your subject with a flashlight.

Get a light meter and experiment and you'll be one up on everyone here.

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Remember also that wattage is a measure of power consumed, and not necessarily a measure of light output (lumens or footcandles).

50 watts of led panels or kino flo will produce more light at the same distance than 200-300 watts of tungsten. Also, color temperature correction using gels have a (sometimes drastic) impact on how much light actually hits the subject. Figure at minimum a 20% reduction when using CTB or CTO gels. Minus Greens will also reduce the usable lumens.

For low budget, 200-250 halogen work lights are a good choice. Adding a dimmer will increase it's usefulness. At full power, halogen color temp runs around 5k, dimming will bring it down to aroud 3800, possibly lower. So, close and dim can give you warm at X lumens on subject, far and bright can give you cool at same X lumens on subject.

GuerrillaAngel is correct. Light behaves just like sound it that it responds according to the inverse square law. Double the distance from the subject, and the light drops off by factor of 4, shorten the distance by half, and intensity increases by a factor of 4. Sometimes moving a light 6 inches has a great impact on image.
 
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The main lights we use are all 500-1000w a pop. We do have a handful of lower wattage bulbs from 100w-250w.

Can't give you a what you should use though unless we're on set. Experiment.

Also, don't forget the 160 ISO rule. It's been said a LOT in your threads by myself and others, but you've been learning a lot and it can be hard to absorb everything at once haha so here it is again:

Use ISOs in multiples of 160 on your Canon DSLR. 160 has less noise than 100, 320 has less noise than 200 or 300, 640 is better than 500, then 800 and 1600.
 
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In my experience, for most smallish interiors you can get by with lights of 500W and below. They'll put out enough light to do the job while being far enough away to stay out of frame. The main issue with work lights, clamp lights, still photo lights, etc... is that it's hard to focus them and control spill. However, they are sure better than nothing. 3 or 4 500W lights on dimmers would probably do wonders for you.

Do some reading on "3 point lighting" which is the basic setup for most things. You can't always do it, and it's not always the best setup, but a good place to start. Key light, fill light, rim light.
 
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If you have lower wattage lights, put them JUST out of frame to light your subject. The inverse of the "farther away takes more light" is that if you move them closer, you can get away with less light (it'll have more of a hotspot though).
 
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GuerrillaAngel said:
I'll let the techies chime in on this, but as physics expert, the further away from your subject(s) your lights are, the more watts you need. It is also possible to blowout the whites of your subject with a flashlight.

Get a light meter and experiment and you'll be one up on everyone here.

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Click to expand...

Hahah!
Yeah, you're right on the nose!
 
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I got to light a shot with 7350 watts in our last shoot, and I've lit with a single 100 watt bulb before. Every shot has different needs. Build a diverse kit at whatever budget level you can, whether scoops, craftsman and ceiling fluorescents or a full Mole-Richardson/Arri kit... variety will be your boon.
 
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