There’s a good chance you’ve been watching television and working at your computer for years in a way that fatigues your eyes, increases your chance of headaches, and decreases your overall enjoyment and comfort. Read on as we show you how to create a comfortable and high contrast viewing experience with bias lighting.

What Is Bias Lighting and What Are the Benefits?

Before we delve into what bias lighting is and why you’ll benefit enormously from implementing it, we need to look at the mechanics of the human eye to truly understand why bias lighting isn’t just a showy trick, but a useful technique that increases viewing comfort and image quality.

Why Screens Strain Our Eyes

The most important thing to understand is that your eyes work on a system of averages. When you look at something, whether that something is car headlights in the distance, a pretty landscape, or a television screen, pupils dilate to regulate how much light enters your eyes. The degree of dilation is triggered by the average amount of light your eyes take in from the entire scene—not by the single brightest point of light within that scene.

When you watch television or use a computer in a dark room, your eyes stare intently at a small window of very bright light that is floating in the sea of darkness around the screen. Your eyes accurately perceive the screen to be very bright in relationship to the rest of the room. However, your eyes don’t adjust to the average level of brightness displayed onscreen. Instead, they adjust to the average brightness across your entire field of view.

This actually causes two problems. First, you’re not seeing as clear a contrast onscreen if the rest of the room is dark. Your eyes will perceive richer dark areas if the surrounding field of vision is not as dark.

Second, and more important, your eyes can become rapidly fatigued. With extended exposure, you’ll likely experience dry or watery eyes, general discomfort, and even tension headaches radiating out from the temple area. In worst case scenarios, with extended exposure some people experience ocular migraines—visual disturbances or even extreme headaches that result from intense eye strain.

Fortunately, despite the fact that your mother might have insisted watching too much TV or TV with the lights off would make you go blind, the effects of such eye strain are temporary and within less than a day of exposure, the symptoms of dry eyes and fatigue should resolve themselves. That doesn’t mean you need to endure it every time you use your workstation or watch a movie on your beautiful new HDTV, though.

Bias lights can help a lot.

How Bias Lights Relieve Strain

So, how do you avoid the inevitable exposure to bright light while viewing your TV or monitor? The key is to increase the general luminance in the room without introducing problems that arise from just indiscriminately flipping all the lights on.

Let’s look at this 3D mockup of a pretty typical living room setup to illustrate how common lighting configurations are problematic for screen viewing (although this mockup is centered on an HDTV, the same lighting problems apply to workstations too).

In your typical living room or workspace, you have ceiling lights, floor lamps, and table lamps—all of which are typically located either above or, in the case of maps and accent lighting, in front of the screen at roughly the same height as the viewer’s head.

Turning on these lights while watching TV does in fact mitigate the issue of the bright screen framed against a very dim room. However, it introduces a whole new host of problems. Lighting that is to the side or behind the viewer projects light onto the viewing surface. This decreases contrast, introduces glare and haze to the image, and creates its own kind of eyestrain as a result. It may not be as intense as the kind of eyestrain you get staring bleary eyed at a bright TV in the dark, but it’s eye strain nonetheless—and it makes the picture look worse, to boot.

Unlike regular lighting, bias lighting is placed behind the screen you are viewing. This raises the surrounding light levels in your viewing area without shining light toward your eyes or toward the screen itself. Because the light originates outside of the sight line of the viewer and is not in a direct path to reflect onto the screen, you get all the benefits of increased light in the room without the problems of glare or light shining directly from the source into your eyes.

The Additional Benefits of Bias Lighting

If you still need some convincing that extends beyond saving your poor eyes from fatigue, then consider two other great benefits. First, the additional indirect lighting provided by the bias lighting increases the contrast of the on-screen image, making your picture look better.

Refer to the optical illusion image above to see the effect made apparent. The bar that stretches across the center of the image is one constant shade of gray (RGB: 142, 142, 142) but it appears to be lighter in on the dark side of the gradient and darker on the light side of the gradient. This illusion, known as the simultaneous contrast illusion, illustrates how your eyes perceive gray to be darker and richer when seen against a lighter background (on the right side), but more washed out when seen against a dark background (on the left side). Illuminate the wall behind your screen and the same contrast illusion takes effect: the grays and blacks on your screen appear richer, and the contrast seems stronger between them and the surrounding area.

Related to that previous trick, many people adjust the values for brightness and contrast to higher levels in order to get the intensity of color and black contrast they desire. If the environment you’re watching the screen in already helps boost the contrast and create a better looking image on the screen, then you can turn the brightness back down. Not only will your eyes thank you because the screen isn’t shining at your face like a headlamp, but you’ll extend the life of the backlight mechanism in your HDTV or monitor.

Eye fatigue reduction, better looking images, and a longer life for your monitor’s backlight? What’s not to love about bias lighting? Let’s take a look at how to set it up so you don’t have to live another day with screen-induced eyestrain and washed-out pictures.

How to Select and Set Up Bias Lighting

At this point you’re probably thinking “okay, okay, you’ve got me. Bias lighting sounds great, and I want it. Just tell me how much it costs so I can get over the shock.” Fortunately for you, it’s really cheap to implement a perfectly functional bias lighting system.

Don’t get us wrong, there are very pricey ways to go about doing it (such as purchasing a Philips TV equipped with their custom color-shifting bias lighting Ambilight system) but there’s absolutely no need to incur such expenses when there are plenty of inexpensive alternatives.

First, let’s break down what makes for a good bias light and why. Then, let’s look at some economical DIY and off-the-shelf solutions.

Selecting a Bias Light

The most important thing to consider when selecting a bias light for your television (aside from the physical consideration of whether the light actually fits behind the screen) is the color temperature.

Light bulbs have a color temperature listed using the Kelvin Color Temperature Scale. The lower the number, the warmer and more red the light; the higher the number, the cooler and more blue the light. Candle flames are 1,900K. They are very warm and cast a reddish/yellow light. Standard incandescent light bulbs are approximately 2,800K and are still quite warm. “Cool White” or “Daylight” bulbs have color temperatures ranging from 5,000-6,500K.

While any bias lighting is better than no bias lighting as far as eye strain is concerned, if you want bias lighting that not only relieves your eye strain but actually makes the content you’re viewing look better, you’ll need the right bulb. You want a bulb temperature that is as close as possible (if not identical) to the reference point used in the industry that both manufactures the screens you’re looking and creates content for said screens. That temperature is 6500K.

The bulbs (be they CFL or LED) inside your HDTV or monitor are calibrated to 6500K. The film and digital video is color corrected to have a 6500K white reference point. The editing suites where content is edited and worked on have 6500K bias lights. Regardless of whether you use a fluorescent tube light, a strip of LEDs, or an incandescent light bulb, you want one with as close to a 6500K color temperature as you can get if your goal is to maximize the quality of the on-screen image.

This immediately rules out the majority of lighting we use around our homes, as there is a distinct consumer preference for warmer light. What makes for a homey and warm feeling in your abode makes for a poor bias light.

Picking a light with the right color temperature is likely all you need to do. However, if you’re dead set on getting the absolute best picture possible you may wish to also look at the Color Rendering Index (CRI) of the light bulb. This number is rarely listed on bulbs intended for household use, but with some careful digging (or by purchasing bulbs intended for hobby or commercial applications where the CRI is important) you can find the CRI value. A CRI of 90 out of 100 or above is the minimum you should aim for if you’re looking for maximum color clarity on your HDTV or computer monitor. This is definitely the province of people looking for an absolute picture perfect experience as opposed to simply relieving eyestrain. So unless you’re building the ultimate home theater setup—or you’re looking to break into video editing—you needn’t stress about getting a perfect CRI-rated bulb. A quality bulb with a 6500K color temperature is more than enough for just about everyone.

Simple DIY Solutions

When we first started searching for a solution to our marathon gaming and Netflix sessions leaving us with burning watery eyes we opted to immediately deploy DIY solutions based on materials we had laying around the house. Better to see if the bias lighting even helped than to spend a bunch of money on a fruitless project.

If your television set or monitor is separated from the wall by some distance, it’s easy to place a regular lamp assembly behind the screen.

In our case, we grabbed a simple and cheap metal shop lamp with a clamp attachment and then popped a daylight temperature LED bulb into it. The whole assembly shines light up into the space behind the large HDTV and diffuses it along the walls. This is a great solution for people with large sets because it uses the wall as a diffuser, requires only one bulb, and provides total coverage for even 65″ screens and larger.

While we’re perfectly happy with the setup (it would only cost around $18 if we didn’t already have the around), there are ways to upgrade the experience while still keeping the project fairly inexpensive. For example, you could purchase a daylight fluorescent bulb intended for reef aquariums and lizard keeping. A good bulb with 6500K color temperature and a 90+ CRI rating runs about $25. Add in a simple lamp assembly to mount it for around another $20, and for under $50, you can have pretty close to what they use in professional studios without shelling out loads of money for the experience.

Again, in the use-what-you-have category, we rigged up our multi-monitor stand with some IKEA Dioder LED puck lights we had laying around. A simple set of four pucks and a little power brick assembly will run you around $25 at IKEA. We’re including this not because the Dioder line has perfect color temperature (they don’t) but to highlight what you can accomplish just using materials you have around the house. If nothing else, it will tell you if bias lighting is right for you.

Although we originally intended to upgrade the bias lighting on both the HDTV and workstation after establishing that bias lighting relieved our eyestrain and other issues (which it absolutely did) we’ve found our simple DIY solutions have worked well enough that any major upgrades or enhanced DIY projects are now more a matter of cosmetics and perfectionism than necessity.

Commercial Bias Lighting Solutions

If you’re just looking for a solution that you can buy, plug in, and go without worrying about matching bulbs or purchasing your own lamp assemblies, there are more than a few solutions available at very reasonable prices.

The cheapest and easiest solution we recommend to anyone who asks is the Antec Bias Lighting for HDTV kit. For around $10, you can get a strip of LEDs big enough for a 60-inch TV (and you can get a two-pack for bigger TVs). They are 6500K color temperature, and include everything you need right in the kit. The LED strip is bright and easy to trim, with pre-marked points where you can safely cut it to remove extra LEDs. Best of all, the thin LED strip works just fine even if your TV is mounted directly to the wall, leaving no space for a regular lamp.

The entire assembly is USB powered so you can, if you wish, drive it off your HDTV set’s USB port so that the bias lighting automatically turns on with the set. Overall, it’s the most compact and easy to install solution we’ve come across that doesn’t require soldering or a bulkier DIY solution with a larger lamp assembly.

Another solution (and the one which should be considered the gold standard for bias lighting) is to buy a bias light kit directly from CinemaQuest—the company that produces bias lights for professionals. You can pick up a their Ideal-Lume Standard light (for screens that are not wall mounted) for $65. Their Ideal-Lume Panelight (intended for wall-mounted screens) runs around $95. This setup runs a fair bit more than a DIY arrangement or LED strip, but for the price you get a custom bulb with 6500K color temperature, a 90+ CRI rating, and a lamp assembly designed for easy installation and adjustment.

Ultimately, it’s so easy to use bias lighting to banish eyestrain, headaches, dry eyes, and other symptoms caused by bright-TV-in-dark-room viewing that it truly makes no sense not to do so. The only thing standing between a comfortable viewing experience with high contrast, crisp colors, and no eyestrain is a light bulb and a little bit of installation work.