Points in Focus Photography

Continuous Lighting Technologies: An Overview

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Video doesn’t really change the conceptual nature of lighting. What it does change, is the type of lighting you need to use. Flashes are out; continuously lighting is in, and with that comes a number of considerations that may not seem obvious at first glance.

For starters, video demands light, lots of light. So much so that I’m frequently surprised by just how much light is needed. For example, a single diffused 50W CFL (~200-250W Tungsten equivalent) in a softbox placed 2-4 feet from a subject will generally give me an exposure around 1/50th f/5.6 ISO 1250. With a full frame or APS-C VDSLR that doesn’t give an awful lot of depth of field to work with, without pushing the ISO up even higher.

Light, well the power requirements can pose real problems in a small studio environment, depending on the choices you make.

Types of Lights

Tungsten

Tungsten is by far the cheapest option in terms of initial costs, and the incremental costs aren’t stifling on an ongoing basis. 250W and 500W lamps run from $4-8 apiece and last for 60-200 hours. Fixtures designed for those lamps can be as inexpensive as a $5 hardware store work light, or a $35 Smith-Victor Adapta-Light.

The biggest advantage to tungsten is that since it’s a black body radiator it produces light in the same way cameras expect light to be produced. That is there aren’t any peaks or gaps in the color spectrum. This leads to generally the best color reproduction you can get compared to LED and fluorescent sources.

On the other hand, the real problem with Tungsten is that 70% of the energy used by the light is emitted as heat. Lighting a subject with 1000W of tungsten light and it gets very uncomfortable being in front of the lights very quickly. The heat load translates directly to increased cooling requirements, and increased power requirements—1000W tungsten lamp on a 120V circuit draws 8.3 amps, meaning you can only put 2 on a 20-amp circuit.

Tungsten can be a real attractive option for getting a very low budget studio up and running, due largely to the relatively small initial costs. That said, as attractive as the costs sound, the heat and power draw factors quickly become problematic. If you’re working in a “converted” bedroom for example, you may only have 1- 15-amp circuit to work with, and a small room will get very hot very quickly with even only a couple of 250W lamps running.

HMI

Hydrargyrum medium-arc iodide, or HMI as it’s known is a vapor arc lamp that’s widely used in larger scale productions due to the efficiency of its output and that it’s daylight balanced. An HMI lamp produces about 4-5 times more light for the same input power compared to a tungsten lamp. Though the spectral efficiency making the situation even more lopsided. At daylight color temperatures, a HMI lamp can be 16 times more efficient than a CTB gelled tungsten lamp; at tungsten color temperatures, a CTO gelled HMI lamp is about 8 times more efficient than an ungelled tungsten lamp.

That said, as attractive as it might make HMI sound, the capital and operating costs are significantly higher than any of the other options, making them largely useless for the low-budget studio.

Fluorescent

Fluorescent lamps have been making inroads in the video production market recently, they are considerably more efficient at producing light than tungsten is, and as a result draw considerably less power and produce considerably less heat. My experience has been that standing in front of 500W of CFL driven light sources isn’t any hotter than standing in a dark room.

Fluorescent lighting has two main drawbacks, color reproduction, and for the low-budgeter upfront costs.

Fluorescing lamps produce a color spectrum that has large spikes in various colors that doesn’t conform to the way cameras expect to see the world. Lamps with a CRI in excess of 95 can do an acceptable job but there are still places where they can and will fall down. I’ve done some testing with CFLs and color rendition here and here.

On the other hand, if you can live with the color reproduction issues that can crop up, you can get quite a bit of power out of not a tremendous amount of electricity. A 50W CFL is roughly equivalent to a 200W tungsten lamp. On a 15-amp circuit, you can power more than 20 of those lamps, giving you the equivalent of somewhere in excess of 4000W of tungsten based light.

The second issue, and it only really effects low-budgeters, is upfront costs. Upfront costs can be considerably higher than for tungsten lights. A 2 lamp Smith Victor FLO fixture is $300, and a 6-lamp F.J. Westcott TD6 Spider Lite $420. Moreover, lamps run $20 to $50 depending on wattage. However, in the long run you’re looking at a fraction of the costs in electricity, cooling, and lamps.

LED

LED is the newcomer to the photographic/video lighting world, and well the world of lighting in general. LED lights have some huge advantages in terms of power and longevity. That said, they do suffer some from some of the same issues in color reproduction that fluorescent lamps do, as well as the potential for significant upfront costs.

Power and heat wise, LED systems draw less than fluorescents and produce more light. A 40W LightPanels 1×1 is rated as the equivalent of 200W of HMI or 500W of tungsten by their measurements. On the other hand, a panel of that size from Lite Panels costs between $1200 and $1800.

There are low budget alternatives to the professional grade panels, for example, Cowboy Studio makes a number of LED lite panels in various sizes, up to 1’ x 1’ like the Lite Panels products at a much lower $500 or below price point.

Number of Lights

Lighting a video set isn’t especially different than lighting a stills one. You still need to light the subject, or subjects, as well as the workspace (if there is one) and the background.

For the subject, or subjects, you really will want a 3-point lighting setup, so plan on at least 3 lights for 1 subject, and more for more subjects.

While I’m on the subject of lighting people for video, I’ve found 2 things in my testing so far. First is that you really do need the hair/separation light. Not having one dramatically impacts the readability of the scene, and can easily result in your subject disappearing into the background. This is especially important if you’ve elected to use a plain black background. Even if you choose your wardrobe such that it doesn’t blend into the background, having the separation light adds a tremendous amount of pop to set your subject off.

Secondly, while you can get away with replacing the fill light, with a fill card, especially if you’re going for a dramatic look, it’s also considerably harder to control and manipulate than a controllable light source.

In addition to lighting your subject, you’ll need to address lighting the set. How many more fixtures this requires varies based on what you actual set and shooting will be. This topic could actually be a full post in and of its self.

That said, for an interview like setup in a real room, I’d consider having at least 2 additional fixtures to light the background beyond the subjects. The same 2 fixtures would likely also be sufficient if you’re lighting a printed/painted backdrop.

Green screens pose a slightly more difficult problem, as they need to be lit more evenly. You can almost get away with 2 fixtures for lighting a small green screen, but it may be real touchy. You could use long (4’) florescent fixtures (more than 1 depending on how big your background is) along the bottom aimed to light the background.

For a basic setup with a single person in front of a background or green screen, much like what I’m doing, you’re looking at somewhere between 4 and 7 fixtures.

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