How many foot candels do I need?

[Dusty Sullivan]

Ok. I am not even sure how to start this question but I need to know how much light I need to shoot with my desired settings at certain distances.

So, if I would like to shoot 1/48th, a320, between f11 - f5.6. How can I tell if a certain light has enough power to do so at, let's say, a distance of 4 ft? Or a distance of 24 ft?

I have confused myself stupid at this point. It has been years since I have had to think about f stops and shutter speeds much less footcandles. But I am trying to light a few things with some specific settings. And I am looking at renting a couple of lights but I am not sure if they will provide the amount of light I need. I just need a way to determine this by looking at the manufacturers photometrics they've posted. In this case the Joker Bug 800w and the LMT Cinepar 1200w.

Can anyone help me with this?
Thanks,
Dusty

 

[Jason Ing]

Ok. I am not even sure how to start this question but I need to know how much light I need to shoot with my desired settings at certain distances.

So, if I would like to shoot 1/48th, a320, between f11 - f5.6. How can I tell if a certain light has enough power to do so at, let's say, a distance of 4 ft? Or a distance of 24 ft?

I have confused myself stupid at this point. It has been years since I have had to think about f stops and shutter speeds much less footcandles. But I am trying to light a few things with some specific settings. And I am looking at renting a couple of lights but I am not sure if they will provide the amount of light I need. I just need a way to determine this by looking at the manufacturers photometrics they've posted. In this case the Joker Bug 800w and the LMT Cinepar 1200w.

Can anyone help me with this?
Thanks,
Dusty

Do you have a light meter?

 

[MJ KERBER]

Remember this rule:

100 asa needs 100 fc to get a f2.8 (24fps / 180 degree shutter)

Calculate from there...

i.e. 200 asa would need 50fc to get f2.8

So, 320 asa needs 125fc to get f5.6, 250 for f8, 500 for f11

 

[Dusty Sullivan]

You're a genius. Thank you so much. That is exactly what I was looking for.

 

[Esmaeil Neisi]

Well i think for digital there's another way,
look at your waveform and increasing the light to have the skin tones on some thing around 45 to 50 IRE. hope that help you

 

[Steve Sanacore]

Arri has a great tool on their web site for calculating fc of their lights at any given distance with many variables. You need to click on a button to go from LUX/Meters to FC/Feet.