Lighting For Paint Correction in Auto Detailing: The Essential Concepts.
By Christopher Brown of OCDCarCare Los Angeles – OCDCarCare.com– 17 April 2014
In the auto detailing community, lighting for paint correction prior to, during, and after the polishing processes is a subject that is casually discussed. These discussions usually contain a few questions about some aspects of light and lighting. However, most discourses tend to lack relevant and necessary information to adequately explore and answer the original topics.
At some point, a large majority of detailers will have a need to supplement or upgrade the lighting in their shops or garages. Mobile detailers will also need to upgrade, requiring lighting that is efficient, sufficient, and portable.
The need for additional lighting usually presents itself on the fly. Consequently, many detailers rush to make a quick purchase, later to find out these lights only really offer more light, not the type of light they truly wanted. The money impulsively spent on a fixture that only provides “more light” is better applied to a lighting system that accurately represents paint’s true state.
The purposes of this article on lighting for paint correction are as follows:
1. To explain the basic concepts behind the science of how light works.
2. To introduce and discuss the factors of light which are most relevant to lighting for paint correction.
3. To enlighten the reader about certain temperatures of light best suited to optimally reveal paint color and defects.
This article will remain as factually relevant to lighting for auto detailing paint correction processes as possible. That being said, basic knowledge of the science of optics (the study of light) lighting systems (light bulbs etc.) are needed for proper analysis. This information will allow an exploration into how lighting can reveal a painted surface, allowing for an analysis of its true condition.
The Science Behind Light: How Light Works
To truly understand light and lighting for paint correction, a basic grasp on some scientific terminology of optics is necessary. Don’t worry- we’re talking basic here!
Although a LOT more information was omitted from this article to keep things simple and short as possible. That being said, if the definitions offered in this article are unclear or insufficient, please take a moment to track down descriptions that enable a better understanding of lighting terminology. This is hopefully the first step in opening the discussion up further within the detailing community.
Light: the visible spectrum of electromagnetic radiation detectable by the human eye. The best example is the earth’s most abundant light source: sunlight.
Definition of the visible spectrum: A very small portion of the atmosphere’s light contain wavelengths visible to the human eye. The groups of violet, blue, green, yellow, orange, and red compose the visible spectrum. These are the only types of wavelengths detectable to the human eye.
Definition of electromagnetic radiation: Energy, light, and heat are all forms of electromagnetic radiation. The term “radiation” is not necessarily cause for alarm because all radiation is not harmful.
The Visible Spectrum of light as contained within the Electromagnetic Spectrum.
The visible spectrum of light is continuous Therefore, each wavelength (color) is not FULLY defined since each wavelength flows into the next.
The chart numbers below display the most accurate scientific approximation of wavelengths associated with each perceived color in the visible spectrum of light.
Every color within the visible spectrum of light operates on a specific wavelength measured in nanometers. The specific bands of color groupings composing the visible spectrum of light are known as the spectral colors (Listed below).
Definition of a light wavelength: Light behaves like a wave. The wavelength of light determines its color. The frequency which light wave move up and down within one second of time is expressed in Hertz (cycles per second).
Definition of a nanometer: 1/1,000,000,000 meter, or one-billionth of a meter.
The Spectral Colors which make up the Visible Spectrum of Light:
|Violet 380-450 nm|
|Blue 450-495 nm|
|Green 495-570 nm|
|Yellow 570-590 nm|
|Orange 590-620 nm|
|Red 620-750 nm|
Most people don’t realize that they are quite familiar with the spectral colors. These are the majority of colors that make up a rainbow. Rainbows additionally contain indigo; a color contained within the visible spectrum, but lacking its own category.
** IMPORTANT Note ** White Light combines of all spectral colors composing the visible spectrum. This is relevant because white light is composed of ALL wavelengths (colors) of light. Sir Isaac Newton first hypothesized and verified this theory by holding prism toward the sun at high noon. The prism filtered the sun’s single white rays of light into each individual spectral wavelength (Violet, Blue, Green, Yellow, Orange, and Red), projecting them them as individual colored beams.
How the Human Eye Interprets Light
Light, at its most basic level, is a wavelength which is assigned a ‘color’ in the human brain. This is the result of a chemical interpretation within the retina of the eye. The retina contains three types of color receptor cones.
- Cone receptors in the eyes detect three wavelength (color) groups.
Long Wavelength Red ~620-750nm
Medium Wavelength Green ~495-570nm
Short Wavelength Blue ~450-495nm
With the RGB (Red, Green, and Blue) cone receptors contained within the retina, the human eye is capable of detecting almost an infinite amount of color combinations. The same sort of technology as a T.V. or smart phone screen—Red, Green, and Blue blend to make all colors of display.
Therefore, when viewing a “color” the human eye is actually viewing a specific wavelength emitted by the colored pigments of an object. It is possible for an object to emit different wavelengths [colors] on the same surface. However, each distinguishable color emits its own distinctive wavelength received by the RGB receptor cones in the retina and coded as a specific ‘color’ in the brain.
This is an important concept in optics because the red of a fire engine is derived from the red pigments contained within the paint. All other wavelengths of light, other than red, contained within the visible spectrum do not appear to the human eye looking at the red pigmentation of the fire truck. Similarly, the leaves of a fern grant the plant its visible color. That color is derived from ONLY the specific wavelength of that particular green.
Light’s Measurable Characteristics
Light’s basic measurable qualities require defining in order to discuss the use of light for illumination. These are the critical terms for discussing lighting for paint correction.
Lumen: The amount of visible light emitted from a singular source. A lumen is roughly equivalent to the amount of light generated by one candle. Basically, Lumens measure the relative intensity (brightness level) of light from a source.
Color Temperature: The perceived color of a light source measured utilizing the Kelvin scale. These include a broad spectrum of colors ranging from deep red, to orange, to yellow, to white, to bright blue. Color values lower in Kelvin temperatures are considered “warm”, containing orange to red light. Colors higher in color temperature are considered “cool”, containing more blue light.
Kelvin Scale: The Kelvin scale (K) is an extension of the Celsius scale. It measures the color of light as emitted from a hypothetical black body (think cast iron stove) when heated to different temperatures. At lower temperatures, it glows red, then orange, then yellow. As the temperature increases, the metal appears white, then blue. The Kelvin scale quantifies the amount of energy needed to transform that black body to each color, assigning numerical values in K.
Daylight: The standard which people consider “normal daylight” is mid-day, when the sun is at its peak in the sky. This light has a temperature of ~5578K, which is slightly on the cool range.
“Normal Daylight” is important to note since the color temperature of the sun changes drastically throughout the day. Light at dawn has a lower color temperature of ~2000K° (very warm –orange/red). Daylight wavelengths quickly increase as the sun ascends in the sky. Mid-day sun has a fairly constant wavelength of~5600K (white/ slightly bluish). Two hours before dusk, light slowly wanes, descending into warmer color temperatures.
Lighting for Automotive Detailing Paint Correction
Now, don’t worry, all of that technical mumbo jumbo is out of the way! So how has this tech talk important or relevant to lighting for paint correction???’
Understanding the science behind lighting technologies aids in paint polishing, “But WHY?” readers may be wondering.
Because, Choosing the Correct Color temperature is VITAL to lighting for paint correction in order to:
1] Detect the accurate representation of the true color value of a surface.
2] Optimally represent, and therefore evaluate the actual of the condition of a surface.
These two variables of lighting aren’t ALWAYS exclusively linked. However, they are applicable discussing color temperatures ~4500K or below. Color temperatures in this range provide poor intensity since they are not close to “pure white,” causing them to cast warm tones onto a surface. Therefore, if a light source casts a tinge of color (a wavelength other than pure white) onto a painted surface; then the true color, and often the true condition of paint defects on that surface, fail accurate evaluations under this lighting.
Warm tones of light are much more forgiving (flattering) of a surface’s true properties. Meaning they do not reveal an object’s every flaw. Incandescent lighting, ~2700K-3300K, is commonplace in U.S. households as ambient (background) lighting for this reason. It is a perfect light to accent skin tones, adding warmth (red tones) which promotes a healthier looking individual.
However, flattering is not a desirable trait detailers want from a surface when lighting for paint correction. Instead, they want that “High Definition–reveal everything look.” This light strikes fear into actresses with freckles, pimples, or age when they appear on modern late night talk shows. Lighting for paint correction at color temperatures between 5000K-6500K reveals everything.
Defining True Color Value for This Article
*** NOTE: ‘True color value’ is relatively subjective to the source of available of light. Therefore, for the purposes of standardization, this article will use sunlight as the best representation of ‘true color value.’
(~5500K) = The average color temperate of the sun’s rays at high noon and for the longest portion of the day. Therefore, ~5500K will act as the standard that displays paint’s optimal characteristics of color and condition.
The sun is the world’s light source, illuminating the majority of automobiles on the planet. Furthermore, ‘daylight’ in this article is defined as the direct rays of the sun as seen in midday. Overcast skies have a totally different color temperatures and light pattern characteristics due to the diffusion of the sun’s rays.
Color Temperature Directly Impacts Evaluation and Results in Paint Correction
To illustrate how important color temperature is to lighting for paint correction; imagine a white vehicle in for full correction.
Light the vehicle up the red bulbs from a photography dark room. What is the immediate result of this lighting? Every surface of the vehicle possesses some shade of red to it. Even the black tires and cowling area will have a significant red hue. Additionally, red lights fail to adequately illuminate any surface of the vehicle in a manner which represent true color properties. No matter how intense [bright] the red light becomes, it can never accurately depict the surface of the white vehicle due to the fact that the ~1500K wavelength casts red over everything.
So why is this relevant? Because, if the human eye is unable to detect the true state of the white painted vehicle BEFORE correction, using a light that casts a color onto a surface, then how would it be possible to identify the true color [and condition] of CORRECTED paint using the same light?
It couldn’t. If red bulbs are the primary lighting source for correction it is nearly impossible to know the current state of correction at any given moment. However, detailers have using lights which inaccurately depict paint conditions for over 30 years!!!
Different Lighting Color Temperatures Drastically Alter the Appearance of Surfaces and Colors
To illustrate how the temperature of a light source affects the illumination of a subject, examine the pictures below. Both photos taken in a pitch dark room.
This writing sample was written upon a blank 8½” x 11″ sheet of plain white paper. The same led light source illuminates both photos. The reason the photos appear different is due to the wavelength (color) of the individual bulbs used to light each photo.
The paper illuminated with the VIOLET LED light, at about 12000°K, masks the true color nature of the paper and the ink. The violet light taints the color perception of everything it illuminates, making it near impossible to discern the true color nature of the paper and ink.
The sample in the second picture utilizes a WHITE LED light, at ~5000°K. Note the major optic differences between the photos! In the second picture, the paper appears its genuine white color and the ink depicts its true red color. This is because white light utilizes all of the wavelengths within the visible spectrum to illuminate a subject. With white light there is no “color” tinting of the object of illumination. Instead, subjects under white light reveal their true color value.
Starting to see where this is leading?
The Kelvin Scale and Color Temperatures of Common Light Sources
The Effects of Lighting for Paint Correction with A Non White Light Source
Illuminating paint with a light source deviating from “pure or neutral white” will not accurately represent the color and/or surface conditions. Precise appraisal of paint condition is never obtained if the color is not depicted accurately. Using a non ‘pure white’ light for paint correction doesn’t allow the current state of a panel a true evaluation at any point during the polishing or evaluation process. For this reason, detailers of the past HAD to move vehicles outside and inspect them in sunlight. The white nature of the sun’s rays provided PURE optic values; allowing the vehicle’s surfaces display their true color and defect natures.
The lower the Kelvin value of a light source, the worse the representation the optic values of a surface. Therefore, a Halogen light at ~2700K is one of the worst sources for providing true surface color and condition values because of low intensity and orange tinting. A marginal improvement is the standard CFL (compact fluorescent lighting) ranging from about ~2700-4200K, which can have varied color tinting. However, LED lighting ~5000K-6500K is near optimal for exposing true color and defect values on vehicle surfaces.
If readers are lost regarding how lighting with a ‘pure’ white light is vital when lighting for paint correction, then please refer back to the example of illuminating a white car with the red bulbs from a photography dark room. [see Lighting for Paint Correction header above] Would it ever be possible to truly evaluate and an accurately estimate paint correction on paint only seen in darkroom lighting? Why not? Paint’s true color value or surface defects are nearly impossible to see if a light is drastically tinged with red.
Why Halogen Lights Fail Horribly for Paint Correction in Auto Detailing
Here is another example. Imagine using a standard halogen work light to inspect the condition of a dark colored vehicle inside a dark room. Note the appearance of the vehicle’s color and the condition of the paint. Next, move the same vehicle outside and inspect it in the sunlight of high noon. Which light source will better represent the true condition and color properties of the paint; the halogen light or the sun? The sun will win every time! Why is this? Because the mid-day sunlight is much closer to a pure white light at ~5500°K. The halogen work light operates at ~2700°K which has an orange hue to it and masks paint values.
Yes, the relative light intensity of the mid-day sunlight is MUCH higher in brightness, (luminosity reading) coming in at 100,000 lux. However, the brightness of a 1000w dual halogen work light, emitting 16,000 lumens, provides MORE than an ample amount of light to show all defects in a painted surface at a distance of 8 feet or less. So why does it fail in comparison to show all defects if its brightness isn’t the issue?
Halogen lights generally fail compared to the sun because the work light’s color temperature of ~2700°K casts an orange hue, tainting the all surface colors of the vehicle. This orange hue doesn’t all ow the human eye to accurately identify true color values. The relative intensity of ~2700K light is low, inhibiting it from revealing the true defect nature of the surface.
The color properties and paint condition of a vehicle are not only revealed by the intensity [brightness] of a light source. However, the further away a light source is from a pure white, the characteristics of a surface illuminated by such a light will be inaccurate.
Mixed Lighting Sources & Varying Color Temperatures for Paint Correction
In a room with mixed lighting sources; meaning lights with differing color temperatures. The intensity of paint correction lights need to be higher than any ambient lighting. For example, if the overhead lights 8 feet above are casting 4000 lumens of light [@ 3800K], then a 300 lumen handheld LED light[@ ~5000K] will only provide true paint illumination when held about a foot or two from the surface. Correction lights only reveal true paint color and surface conditions if all ambient lighting values are less than the correction light.
Light at ~5000K is optimal for identifying true color value since it is closest to “pure white.” Light at ~6500K may sometimes better show surface conditions and paint defects. Light at 6500K has a greater relative intensity, revealing more defects. When comparing these color temperatures, a 6500K light appears significantly cooler [bluish] than a 5000K light, because the 6500K light will slightly tint the vehicles color with bluish light. For practical purposes this is not nearly as significant as the warm tones that a halogen bulb emits at ~2700K. Because the 6500K bulb has a much higher relative intensity, allowing it to reveal all surface defects on paint.
Optimal lighting for paint correction differs from vehicle to vehicle in order to reveal true colors and surface conditions. It has been stated that to achieve optimal lighting on a wide variety of vehicles, an individual may wish to consider two sets of bulbs. One set at 5000K and another at 6500K. The 5000K bulbs better capture the paint’s true color value since it is closest to color neutral. The 6500K light may maximize the ability to better detect certain defects. Different vehicle colors are prone to displaying defects differently due to the color wavelength of the surface. Overall though, 5000k is the best color temperature to view the majority of automotive paint color values and defects. Instead of changing the bulbs, consider altering the overall intensity (brightness) of the light source — depending on the paint color.
Closing Summary on Lighting for Paint Correction
In closing, remember; white light is the combination of all colors in the visible spectrum to the human eye. This is why it naturally appears to be the ‘brightest’ and thus purest wavelength of light. For this reason, white light is best for true illumination of any object including lighting for paint correction. White light casts a continuous spectrum, projecting all visible wavelengths onto anything it illuminates. True color value and condition of an object are accurately depicted only when the entire visible spectrum of light is cast upon said object. This is particularly important in paint correction because it allows the detailer to identify the true color of the paint and condition of surface defects for accurate evaluation and correction during the entire process.
~keep on buffin.
© Christopher Brown of OCDCarCare Los Angeles – OCDCarCare.com – 2014
Whew, that was a lot to process! Perhaps SOMETIME in the future: Pt. 2 – Comparing Lighting Technologies for Paint Correction.
For more interesting topics on: auto detailing, paint polishing, and car care please browse: OCDCarCare Los Angeles’s – Detailing Article Archive.
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