Jump to content


Photo

Measuring Light Output

exposure preproduction film cinematography footcandle lux light measure

  • Please log in to reply
3 replies to this topic

#1 Jacob Mitchell

Jacob Mitchell
  • Basic Members
  • PipPip
  • 32 posts
  • Student
  • Boston

Posted 12 September 2016 - 06:59 PM

Hi All!

 

As a student, each projects means a way to stretch myself further. If I'm not trying something new (or a little bit scared) on a project then I feel like I'm not taking steps forward. 

 

Lately I've been doing pretty in-depth floor plans and 2D pre-vis, and it has been working wonders for every project. However, I'm still working to get exactly what I want in my head to paper, so that on set my images are not a surprise. 

 

Is there a way I can tell how many foot-candles a certain light will output? I'm wanting to essentially know exactly how powerful a light I'll need to expose to a pre-determined f-stop. I'm familiarizing myself with inverse square law, so all I'd need is an output at any one distance and could work from there. 

 

Is this just a knowledge gained from experience? Or is there a practical way to determine output? 

 

Thanks,

Jake Mitchell


  • 0

#2 Jacob Mitchell

Jacob Mitchell
  • Basic Members
  • PipPip
  • 32 posts
  • Student
  • Boston

Posted 12 September 2016 - 07:08 PM

Here's an awesome spreadsheet of different measurements, spot and flood, at 20 feet.

 

http://wolfcrow.com/...sComparison.jpg


Edited by Jacob Mitchell, 12 September 2016 - 07:09 PM.

  • 0

#3 John E Clark

John E Clark
  • Basic Members
  • PipPipPipPip
  • 823 posts
  • Other
  • San Diego

Posted 13 September 2016 - 11:22 AM

Hi All!

 

As a student, each projects means a way to stretch myself further. If I'm not trying something new (or a little bit scared) on a project then I feel like I'm not taking steps forward. 

 

Lately I've been doing pretty in-depth floor plans and 2D pre-vis, and it has been working wonders for every project. However, I'm still working to get exactly what I want in my head to paper, so that on set my images are not a surprise. 

 

Is there a way I can tell how many foot-candles a certain light will output? I'm wanting to essentially know exactly how powerful a light I'll need to expose to a pre-determined f-stop. I'm familiarizing myself with inverse square law, so all I'd need is an output at any one distance and could work from there. 

 

Is this just a knowledge gained from experience? Or is there a practical way to determine output? 

 

Thanks,

Jake Mitchell

 

ARRI has an on line calculator and an iPhone App (perhaps a Android one as well...) which lists their light products' output at various distances.

 

The actual lux/footcandles delivered by an arbitrary light depends on a number of factors, reflector shape, lensing if any, etc. Many off brand light producers only list the wattage of the lamp itself, which doesn't directly give 'how much light is falling on the subject'.

 

I'd suggest getting a light meter that reads out lux/fc, and finding a rental house that has a selection of various lights and measure them.


  • 0

#4 Adrian Sierkowski

Adrian Sierkowski
  • Sustaining Members
  • 6885 posts
  • Cinematographer
  • Los Angeles, Ca

Posted 13 September 2016 - 10:43 PM

To be honest; I normally ballpark off of the Arri Estimates for most things-- the issue of moving a light a little closer or using a scrim it in are pretty academic if you ask me. I haven't seen the arri photometrics as an android app, but i did save the page to my homescreen, so i have it whenever (data connectivity permitting).

With time, though, you'll just kinda know.


  • 0



Tai Audio

ZoomCrane

CineTape

Zylight

Glidecam

Willys Widgets

Abel Cine

FJS International, LLC

Metropolis Post

Visual Products

Gamma Ray Digital Inc

Rig Wheels Passport

Pro 8mm

The Slider

Paralinx LLC

Ritter Battery

Quantum Music Works

rebotnix Technologies

Aerial Filmworks

Broadcast Solutions Inc

CineLab

Technodolly

Willys Widgets

Zylight

Metropolis Post

Rig Wheels Passport

Paralinx LLC

FJS International, LLC

Gamma Ray Digital Inc

The Slider

Quantum Music Works

Broadcast Solutions Inc

Glidecam

Technodolly

Abel Cine

ZoomCrane

Visual Products

rebotnix Technologies

Tai Audio

Ritter Battery

CineTape

Pro 8mm

Aerial Filmworks

CineLab