Using a light booth to visually judge color is a great start to a successful color evaluation program. It allows you predict how color will look under multiple light sources so there won’t be any color surprises when the light changes over the life of the product. Introducing a color measurement device to capture spectral data is the next logical step.
For a really great color program, you need to use both a light booth AND a spectrophotometer. This dynamic duo offers benefits you can’t achieve by using just one or the other. Today we’ll explore how to combine these two methods of color control to ensure your evaluation program is a gateway – not a roadblock – to your overall color success.
Benefits of a Light Booth
Lighting has everything to do with how color looks. Light booths can simulate many different types of light so you can clearly see how a color will react to different lighting conditions. Light booths are commonly used to compare a standard and a sample, or to evaluate how adjacent parts will look when assembled, under every possible light the product may encounter in the real world.
Benefits of a Spectrophotometer
A spectrophotometer can measure color to see how much light is reflecting at each point across the visible spectrum for that light source. This mix of reflected light is what creates color.
Here are the reflectance curves for daylight (CIE D65), cool white fluorescent, and incandescent (Illuminant A) lighting. Notice how incandescent has a lot of energy in the red area, but not much in blue. Because of the increased energy in the red area, objects illuminated by incandescent lighting will appear redder than those under daylight or cool white fluorescent.
By measuring the amount of reflection across the visible spectrum, a spectrophotometer can provide a reflectance curve, an exact fingerprint, for each color. This is the most precise way to identify, communicate, and evaluate color.
Three Reasons You Need a Light Booth AND a Spectrophotometer
If a light booth and spectrophotometer are each so effective on their own, why do you need both? Here’s why.
1. Color is subjective.
Light booths have some limitations. The color one person thinks is acceptable may be an obvious fail to another. Background effects can play tricks on your eyes and affect the color you think you see. Since a spectrophotometer only views and measures the reflected light from the targeted sample area, it cannot be tricked by the environment, and it is not subject to human deficiencies. As one of our customers so wisely said, “A spectrophotometer never has a bad day.”
2. Visual evaluation cannot always identify metamerism in the absence of a lightbooth.
Metameric pairs are shades that appear to be identical under a single specified lighting condition but actually have different fingerprints, resulting in the colors looking different under different lighting sources. Obtaining the reflectance curves from a spectrophotometer measurement is the only true way to identify metamerism.
This graph shows two colors that match under D65 lighting (daylight) but not under incandescent light. That means if you see these two colors together under noon daylight, they will appear to match. But once you come inside under a reading lamp, you’ll notice they’re actually different colors.
This picture shows the same dyed wool swatches under U30 fluorescent (top) and A incandescent (bottom) light sources. Notice how much the colors change? Metamerism can be caused by using different materials, different dyes, different colorant formulations, etc. You can learn more about it here.
3. Even spectrophotometers can have limitations.
Although the data they collect is scientific, using an improperly calibrated device or the wrong devices settings can lead to incorrect color measurements. Visual evaluation, in combination with spectral measurement, is the best way to ensure each color “looks right.”
Tips for Evaluating Color Visually AND Instrumentally
When using both devices together as part of a more holistic evaluation program, there are three additional things you need to do.
1. Follow visual evaluation best practices.
Do you see any numbers in these two colorful circles of dots? More specifically, you should see a number “6” in the first circle, and a “2” in the second. If you don’t, you may want to consider taking a color vision test.
Even if you can see the numbers, how acute is your color vision? The Munsell FM100 Hue Test is the best way to find out. Color is highly subjective, and there are many pitfalls to watch out for. Be sure to color test everyone who is visually evaluating color, and when color is in question, bring in another set of eyes.
2. Choose the right spectrophotometer for the job.
Spectrophotometers come in a range of sizes, from portable devices to large benchtop instruments, and can measure just about anything, including liquids, powders, plastics, paper, metal and fabrics. There are three primary types: 0º/45º (the most common), sphere, and multi-angle. Your selection depends on application, the type of material being measured, desired functionality, and portability.
Here’s help for choosing the best spectrophotometer for your needs.
3. Sync the illuminant settings in your spectro and light booth.
We get a lot of calls from customers who can’t understand why their spectral numbers and visual evaluation don’t match. The spectro may say the color is too dark, but it looks right in the light booth. Or vice versa… the device says the color is dead on, but visual evaluation shows it clearly isn’t.
This mismatch is usually caused by measuring under one set of lighting conditions, then viewing under another. It’s common to measure under D65 (daylight illumination) in industries like paints, plastics, and automotive. But unless your lab is illuminated with daylight bulbs, you likely won’t see the same color you’re measuring without a light booth set to D65.
Be sure to select the same illuminant in your device and your light booth.
Set Yourself Up For Success!
If you’re visually evaluating color, we recommend adding a spectrophotometer to capture spectral data. If you’re measuring color, we recommend having at least one light booth available. When used together correctly, these two tools can take your color evaluation program from good… to great! Get in touch if you need help choosing the best solutions for your specific needs.