A Comparison of Light Fixture Output and Photometrics (Part One): Tungsten

Ever enjoyed the frustration of trying to compare photometric or light output data (footcandles, lux) between two or more light fixtures? Here’s me taking away the pain (at least a lot of it).

In this first part we cover major tungsten/halogen/quartz light fixtures (3200K) from the following manufacturers:

  • Arri
  • Mole Richardson
  • Lowel
  • Ianiro
  • Dedolight
  • Desisti
  • Profoto
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If I’ve left out your favorite manufacturer or fixture, please forgive me. As far as I know there isn’t a similar comparison anywhere on earth, so I’m entitled to the most amount of mistakes.

What are we comparing? The following:

  • Footcandles/Lux at 20 feet.
  • Comparison of light output in stops (how useful!) to a gold standard (I wonder what that might be?)
  • Light output in Lux per watt, to see which lights give the most bang for the buck. No more lumens per watt crap.

The gold standard(s)

The light

So, which light should be crowned the gold standard? I don’t know, so I guess I was free to pick what I thought was the most ubiquitous and widely understood light around, the tungsten fresnel.

Specifically, the 650W Arri 650 Plus tungsten fresnel. Of course, the quality of the bulb matters a lot, so I’ve gone ahead and used the highest rated bulb (in terms of light output).

As a rule of thumb, at 100 ISO/ASA, with a shutter angle of 172.8 degrees or 1/50th of a second, if you use a light fixture that delivers 100 footcandles at a distance of 10 feet, you can get an f-number of 2.8 (f/2.8). However, in the real world, one uses modifiers that cut down this light. The light fixture might have to be placed at 20 feet instead of 10 feet, and that takes away a stop.

The Arri 650 Plus can deliver the following:

  • @1/50th shutter or 172.8 degree angle
  • @20 feet
  • @ISO 800
  • @24fps
  • an f-stop of f/4.
  • Pair it with a modifier or gel that cuts one stop, and you can get f/2.8. Since that’s the f-number I recommend for professional lenses, it’s a great start.

The distance

I choose 20 feet to be the gold standard as far as distance is concerned. Even though the 650W can be used at 10 feet, and you have LEDs and CFLs being used at the same distance, when you use higher wattages, you have to get further away. E.g., if you use a 575W HMI, you cannot place it at a distance of 10 feet (safe distance is about 17 feet). To cover the vast number of scenarios possible, a light should have an equivalent rating at 20 feet. This is also keeping in mind the spaces used in architecture, as I’ve discussed in How to put together a Lighting Kit for Video.

The unit

Footcandles or lux? Both. The analysis is comparing two things: How each light varies in light output compared to the 650 Plus, and what the lux per watt ratings are. I used both for the former, and only Lux for the latter. For two simple reasons:

  • It is the SI unit, as discussed in The Units of Photometry.
  • It is the higher number, so is easier to divide by larger wattages like 12000 and 24000 watts.

Being the gold standard, every other fixture will be compared to the light output of this fixture. This difference is given in stops. You can see quite clearly which lights deliver more or less output than the 650 Plus, and which lights deliver more lux per watt. That’s the goal.

ultimately, every light-type, including HMI, LED, CFL and Plasma, will be compared to the Arri 650 Plus.

Clarifications and caveats

Such a comparison cannot be completely accurate. There are too many types of fixtures, modifiers, bulbs and situations to make this scientifically accurate, so don’t expect it. Furthermore, nobody has the money to buy each and every fixture and modifier and subject them to controlled testing. Therefore, take note of the following caveats:

  • Information in the chart might be inaccurate or plain wrong. For correct data, refer to the manufacturers’ websites.
  • The ratings and figures are taken from the manufacturers’ websites, and no other sources. These ratings are as published by the manufacturers and might not factually bear out.
  • When more than one bulb-type is available, I’ve chosen the one with the greatest output.
  • Many models are left out because I don’t care about them!
  • The red letter in the chart means the distance is below safe limits.
  • Do NOT make decisions based on this chart. Perform your own research. You are solely responsible for your actions.
  • Just because some fixtures don’t show 120 V or 220V doesn’t mean the manufacturer doesn’t make them for those voltages. I couldn’t find info on it, that’s all.
  • The voltages are gross averages. They can range between legally acceptable values, and this will slightly affect photometrics, as I’ve written in How to Estimate if your Lights and Gear will work on Portable Generators and the Mains Power Supply.

The chart

So, how do you read the chart? I’ve divided it between manufacturers and fixtures. I’ve tried to find the footcandle and lux values at 20 feet, but some manufacturers prefer to rate their fixtures at different distances. Therefore, I’ve ‘normalized’ the reading to what it would be a 20 feet. I’ve included both numbers so you can make your own judgements.

Each light is compared to the Arri 650 Plus tungsten fresnel fixture, and the difference is written in stops. Negative stops means lower light output.

The final column lists the total lux output divided by the wattage, which gives us a pretty accurate indication of whether we are getting enough light by increasing wattage. Great comparison (if I say so myself), so I hope you find it useful. Here’s the chart (click to enlarge):

Lighting Comparison Chart

What do you think? Useful?

In Part Two I’ll compare HMI fixtures, and then on to LEDs and CFLs and everything else. Don’t go anywhere.

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7 replies on “A Comparison of Light Fixture Output and Photometrics (Part One): Tungsten”

  1. Great article – deserves more feedback – thanks for putting this together.

    I think in 2018 this really shows the benefits of cameras like the GH5S with it’s native duel ISO. At ISO 2500 a low budget production could light indoor with some ARRI 650’s and get similar light to a far more expensive setup.

    Thanks again for what you put out there – I just discovered your work recently and it’s all fantastic.

  2. “The light fixture might have to be placed at 20 feet instead of 10 feet, and that takes away a stop.”
    Actually, it drops two stops. This is the inverse square law.

  3. It appears that the lux rating for lights at 10 feet have been halved to convert to 20 feet equivalent. Shouldn’t they be divided by 4 to account for the inverse square law ?

    So 1000 lux at 10ft would be 250 lux at 20ft (not 500)? Or am i missing something ?

  4. With tungsten, fluorescents, HMI’s, CDMs and LEDs all competing for the same use, I would think that every single ad or listing for a light should include a universal output metric. But remarkably they don’t. You can go to B & H and see all these lights listed for sale with no indication of the amount of light you get out of them. Lamps usually have lumens listed on the box but how much is lost in the housing? Reflectors, optics and everything else in there has an effect. I’m sure the same LEDs will deliver less light through a fresnel housing that they would bare. So I argue that every light should have it’s real world output in lumens listed. From lumens you can derive flux and foot candles and everything else. It doesn’t do much good to express it in f/stop / ISO Shutter terms, because that would all have to be converted again for each situation.

    1. The problem with Lumens is it doesn’t take into account fresnels, lenses, diffusion, PAR deflectors, glass, and the myriad of other things that make up a light fixture. Not to mention set conditions like haze, rain, bounce, etc. The only output I find useful is the Lux (of Footcandle), but one has to measure it at the actual location.

      Who knows, maybe one day it will all be computerized!

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