The Crayon Trials

New kinds of lighting are more energy-efficient, but they achieve some of that efficiency by sacrificing a complete spectrum, spectral smoothness, good color matching, and color identification. In some cases, two colors that appear different under some lights appear identical under other lights.

This is not really a new problem, but it has become a larger problem with the government ban on incandescent bulbs. Incandescent bulbs could be used to simulate some other sources, but the other sources can't be used to simulate incandescent light, sunlight, northern sky light, or overcast sky light. Halogen light works, but will probably be the next target of the environmentalists. And many lamps labeled "full spectrum" are not really full spectrum.

So how much of a problem is this really? Are colors changed so much that color recognition becomes an issue? That depends on the light source and the particular colorant used. The page author has a forest green umbrella that looks steel blue under an early LED source.

THE TYPES OF LIGHT SOURCES TESTED

Type	Category	Examples	Spectrum Type
0	Natural	Sunlight, Northern Sky, Overcast, Low Sun, Green Grove	Continuous, insignificant dark lines
I	Black Body	Incandescent, Halogen, Constructed Full-Spectrum	Continuous, some have color bias
II	Peaks	Old-style fluorescents, "Full-Spectrum" CFL	Continuous, with bright lines
III	Gaps	Light Emitting Diodes (LEDs)	Dark gaps in spectrum
IV	Few Bright Lines	Mercury Vapor, Sodium Vapor, High Intensity Discharge (HID)	Few or concentrated lines
V	Many Bright Lines	Compact Fluorescent Lights (CFL), Xenon Flash	Spaced bright lines
VI	Lines & Bands	Phosphor CFL	Bright lines & bright bands
VII	Bands	Colored Phosphor CFL	Bright bands
A, B	Combination	Multiple lamp types used	Two or more types, comma separated

PART I - THE EXPERIMENTS

THE CRAYON PROCEDURE

The crayons were used to make a test target sheet with one patch for each color. Each patch has a white area surrounding it and the name of the color underneath. The colors were arranged in color-wheel order in three groups: hues, light colors, and dark colors. Two additional groups were made for the browns, and for the neutrals (black thru white).

The colors that never showed any anomalies (Black, Gray, and Silver) are not listed in the table.

The target is not reproduced here, because RGB or CMY reproductions will NOT behave the in the same way as the original colors behave. Their behaviors will be those of the phosphors on the monitor or the dyes in the printer inks, not the original pigments. Anyone wishing to reproduce the experiment must make a target with an actual box of these crayons.

One other target, a forest green umbrella that shows marked changes in color under different light sources, was also observed. The results are shown where the color seen is a color other than forest green.

Another target was prepared with a CMY ink-jet printer. The results were completely different. This target is discussed below.

The target sheet and the umbrella are then observed under many different kinds of light. Observations were made for color shifts, colors matching where they shouldn't, and unusually light or dark colors. Fluorescence was also observed in some colors under some light sources. The observations are listed below by categories corresponding to the type of light used.

CRAYON RESULTS

spacer
Natural Lights
Type	Light Source	Errors	Anomalies Noted
spacer
0	Sunlight	0	No anomalies noted
spacer
0	Bright Cloudy	0	No anomalies noted
spacer
0	Northern Sky	0	No anomalies noted
spacer
0	Overcast Sky	2	Tickle Me Pink is redder
Tan is yellowish
spacer
0	Low Sun through Thin Cloud	3	Burnt Orange very close to Orange
Tan slightly yellowish
Goldenrod very close to Dandelion
spacer
0	Green Grove (Surrounded by foliage)	6	Magenta same as Violet Red
Scarlet very close to Red
Yellow slightly Greenish
Goldenrod close to Dandelion
Cadet Blue is almost Gray
Forest Green Umbrella is greener
spacer
Incandescent & Halogen Lights
Type	Light Source	Errors	Anomalies Noted
spacer
I	Incandescent	11	Cerulean Blue is much darker
Blue is darker
Indigo is much darker
Blue Violet is darker
Brick Red is lighter
Burnt Orange is much oranger
Goldenrod is much oranger
Cadet Blue is Gray
Purple Mountain Majesty is much darker
Salmon is much redder
White darker than Control
spacer
I	Halogen	5	Blue is darker
Indigo is darker
Blue Violet is darker
Cadet Blue is Gray
White darker than Control
spacer
Old Fluorescent Tubes
Type	Light Source	Errors	Anomalies Noted
spacer
II	Old Daylight Fluorescent	3	Yellow slightly greenish
Goldenrod close to Dandelion
Forest Green Umbrella is Blue Green
spacer
II	Old Cool White Fluorescent	7	Magenta same as Violet Red
Yellow slightly greenish
Tan is yellowish
Goldenrod same as Dandelion
Asparagus is yellowish
Spring Green same as Green Yellow
White same as Control
spacer
II	Old Warm White Fluorescent	7	Macaroni and Cheese is yellowish
Sky Blue slightly darker
Cerulean Blue slightly darker
Cadet Blue is Gray
Mauvelous same as Brown
White slightly bluish
Forest Green Umbrella is yellower
spacer
Compact Fluorescent Lights (CFL)
Type	Light Source	Errors	Anomalies Noted
spacer
V	Daylight CFL	6	Yellow is greener
Robin's Egg Blue is greener
Pacific Blue is greener
Burnt Orange is yellowish
Goldenrod same as Dandelion
Salmon is redder
spacer
V	Daylight CFL Filter	3	Burnt Orange same as Orange
Tan is yellowish
Cadet Blue is Gray
spacer
VI	Daylight CFL Phosphor	1	Salmon is redder
spacer
V	"Full-Spectrum" CFL They lie! They added some blue and violet lines.	3	Yellow is greenish
Cadet Blue close to Gray
White darker than Control
spacer
V	Soft White CFL	16	Yellow slightly greenish
Robin's Egg Blue is greener
Sky Blue same as Turquoise
Pacific Blue same as Blue Green
Cerulean Blue is darker
Blue is darker
Indigo is darker
Blue Violet is darker
Violet is redder
Red Violet is redder
Sepia same as Brown
Cadet Blue close to Gray
Peach same as Apricot
Salmon is oranger
White darker than Control
Forest Green Umbrella is yellower
spacer
Light Emitting Diodes (LED)
Type	Light Source	Errors	Anomalies Noted
spacer
III	Daylight LED	8	Yellow is slightly greenish
Forest Green is yellower
Violet is redder
Tan is yellower
Cadet Blue is Gray
Salmon is darker
Mauvelous is yellowish
Forest Green Umbrella is Blue Green
spacer
III	Daylight LED Filter	6	Yellow slightly greenish
Sky Blue same as Turquoise
Pacific Blue same as Blue Green
Violet Red same as Magenta
Goldenrod same as Dandelion
Cadet Blue close to Gray
spacer
III	Soft White LED	7	Yellow slightly greenish
Green Yellow same as Yellow
Sky Blue same as Turquoise
Red Violet is redder
Bittersweet same as Burnt Orange
Cadet Blue is Gray
Salmon is redder
spacer
Special Combinations
Type	Light Source	Errors	Anomalies Noted
spacer
I (III, VII)	Special Full Spectrum Set*	0	No anomalies noted (comparison standard)
spacer
III, V, VII	Full Spectrum Set* + Daylight CFL	1	Goldenrod closer to Dandelion
spacer
III, VII	Daylight LED and Blue CFL	6	Red is darker
Mac and Cheese same as Yellow Orange
Pacific Blue same as Blue Green
Sepia same as Brown
Burnt Orange same as Orange
Goldenrod same as Dandelion
spacer
III, VII	Soft White LED and Blue CFL	1	Forest Green Umbrella is yellower
spacer
I, III, VII	Full Spectrum Set* + Incandescent	2	Pacific Blue is brighter
Burnt Orange close to Orange
spacer
I, VII	Incandescent + Blue CFL	5	Pacific Blue is lighter
Sepia close to Brown
Bittersweet is yellowish
Asparagus is yellowish
White is yellowish
spacer
III	Mix of Daylight and Cool White LEDs†	1	Forest Green Umbrella is bluer†
spacer
III, V	Mix of Daylight LED and Daylight CFL	3	Yellow has a slight green tinge
Goldenrod closer to Dandelion
Tan is yellowish
spacer
V	Soft White and Daylight CFL	4	Red close to Scarlet
Violet red close to Magenta
Burnt Orange same as Orange
Cadet Blue is grayer

spacer
RGB Sources
Type	Light Source	Errors	Anomalies Noted
spacer
VII	Red, Green, and Blue CFLs	19	Red same as Scarlet	Asparagus is lighter
Red and Scarlet are brownish‡	Periwinkle is darker‡
Apricot same as Mac and Cheese‡	Peach is brownish
Dandelion is Yellow‡	Melon is brownish
Yellow is slightly greenish	Salmon close to Brick Red‡
Sky Blue same as Turquoise	Mauvelous is brownish
Blue is lighter	Gold is greenish‡
Cornflower is darker	Timberwolf as dark as Silver‡
Magenta same as Violet Red	Forest Green Umbrella is Blue Green‡
Burnt Orange is much darker‡
spacer
VII	RGB color monitor producing white light	11	Mac and Cheese same as Yellow Orange	Cadet Blue is Gray
Yellow is slightly greenish	Peach is brownish
Magenta same as Violet Red	Mauvelous is yellowish
Sepia same as Brown	White slightly darker than Control
Mahogany is Red	Timberwolf is as dark as Silver
Goldenrod same as Dandelion
spacer
VII	Blue CFL	49	Violet Red very close to Violet	Brick Red very dark
Wild Strawberry much darker	Mahogany very dark
Red is Black	Chestnut is very dark
Scarlet is much darker	Bittersweet is very dark
Red Orange is much darker	Brown is very dark
Orange fluoresces Yellow	Burnt Sienna is very dark
Yellow Orange fluoresces Yellow	Raw Sienna is very dark
Mac and Cheese much browner	Burnt Orange is very dark
Apricot is much grayer	Tan is very dark
Dandelion fluoresces Yellow	Goldenrod fluoresces yellow
Yellow fluoresces Yellow	Olive is very dark
Green Yellow fluoresces Yellow	Asparagus is very dark
Yellow Green fluoresces Yellow	Tumbleweed looks yellow-greenish
Granny Smith fluoresces Yellow	Spring Green fluoresces Yellow
Green is very dark	Peach is much darker
Forest Green is very dark	Melon is much darker
Indigo is very dark	Salmon is much darker
Blue violet is very dark	Carnation fluoresces Carnation Pink
Violet is very dark	Lavender very close to Violet
Plum is very dark	Mauvelous very close to Violet
Orchid very close to Violet	Gold fluoresces Yellow
Tickle Me Pink very close to Violet	White very close to Blue
Red Violet is very close to Plum	Timberwolf very close to Violet
Magenta is very close to Violet	Forest Green Umbrella is very dark blue
Sepia very dark
spacer
Metallic Arc Lights
Type	Light Source	Errors	Anomalies Noted
spacer
IV	High Pressure Sodium Vapor	30	Red is very close to Black	Violet is very dark
Yellow Orange is Yellow	Plum is very dark
Mac and Cheese is Yellow	Orchid is very dark
Apricot is Yellow	Red Violet is very dark
Dandelion is Yellow	Magenta is bluer
Green Yellow is Yellow	Sepia same as Brown
Green is very dark	Burnt Sienna is darker
Blue Green same as Pacific Blue	Burnt Orange same as Tan
Sky Blue is very dark	Goldenrod is Yellow
Pacific Blue is dark	Olive is grayer
Cerulean Blue same as Pacific Blue	Tumbleweed close to Gold
Blue is very dark	Peach is Yellow
Cornflower is very dark	Melon is Yellow
Indigo is very dark	Salmon is browner
Blue Violet is very dark	Forest Green Umbrella is greenish black
spacer
IV	Mercury Vapor	41	Violet Red is Violet	Sepia same as Brown
Strawberry is Violet	Brick Red is Violet
Red is Black	Chestnut is much darker
Red Orange is browner	Raw Sienna same as Burnt Sienna
Mac and Cheese same as Apricot	Tan same as Burnt Orange
Dandelion same as Yellow	Goldenrod is Yellow
Green Yellow same as Yellow	Cadet Blue is Gray
Granny Smith same as Yellow Green	Purple Mountain Majesty is much darker
Green is very dark	Tumbleweed is greener
Forest Green same as Robin's Egg Blue	Wisteria is Gray
Sea Green same as Yellow Green	Periwinkle is grayer
Sky Blue same as Turquoise	Peach same as Apricot
Cerulean same as Blue Green	Melon same as Yellow Orange
Blue is much darker	Salmon is browner
Indigo is Violet	Carnation fluorescing Carnation Pink
Blue Violet is Violet	Lavender is grayer
Plum is Violet	Mauvelous is gray
Orchid is Violet	Gold is Greener
Tickle Me Pink is browner	White same as Control
Red Violet is more violet, very dark	Forest Green Umbrella is greenish black
Magenta is Violet
spacer
IV	High Intensity Discharge (HID)	17	Red is very dark	Tickle Me Pink is redder
Mac and Cheese same as Yellow Orange	Sepia same as Brown
Yellow is slightly greenish	Brick Red is darker
Sea Green is greener	Mahogany is oranger
Robin's Egg Blue is bluer	Burnt Orange same as Orange
Cerulean is darker	Tumbleweed close to Gold
Indigo is darker	Melon is oranger
Blue Violet is darker	White is darker and yellower than Control
Red Violet is darker
spacer

NOTES

* The Full-Spectrum Set is a light fixture including the following lights:

Soft White LED
Daylight LED
Feit Blue LED (supplies the missing cyan band)
TCP Blue CFL (supplies missing violet and blue-greens)
Feit Red CFL (supplies missing far reds)

Together, these sources provide a nearly flat response with emission at every visible wavelength. This kind of source is no longer commercially available in a single bulb.

Details on the Full-Spectrum Light Source

The Full Spectrum Light Set is the standard to which all of the other sources are compared.

† This situation had the steel blue appearance of the umbrella with an older Daylight LED bulb. Since then, that bulb burned out and was replaced with the newer version shown here.

‡ These entries pertain to only the old red CFL. It was found to be too faint, and was replaced with a brighter red CFL from a different manufacturer.

THE INKJET PROCEDURE

Microsoft MSPaint (the old version from Windows XP, not the useless new one) was used to make a test target sheet with one patch for each color. Each patch has a white area surrounding it and a key for the color names. The colors were arranged in color-wheel order in three groups: 24 hues, 12 light colors, and 6 dark colors. Another group was made for browns, tones, and the neutrals (black thru white).

Black	Brick Red	Red	Vermillion	Orange	Amber	Pink	Apricot
Black	Dark Yellow	Yellow	Chartreuse	Leaf	Lime	Pale Yellow	Spring Grn
Black	Forest Grn	Green	Kelly	Aquamarine	Turquoise	Pale Green	Bluegrass
Black	Prussian	Cyan	Sky Blue	Azure	Cerulean	Pale Cyan	Pale Azure
Black	Ultramarine	Blue	Indigo	Violet	Purple	Cornflower	Orchid
Black	Maroon	Magenta	Heliotrope	Cerise	Carmine	Lilac	Carnation
Gray	Chestnut	Burnt Sienna	Burnt Ochre	Ochre	Gold Ochre	Goldenrod	Black Yellow
Timberwolf	Salmon	Tan	Olive Green	Cadet Blue	Gold	Silver	White

This target is reproduced here in miniature, because it is an RGB image, and is designed to be printed with a CMY printer. These colors DO behave in the same way as the original. Their behaviors will be those of the phosphors on the monitor or the dyes in the printer inks. Anyone wishing to reproduce the inkjet experiment can enlarge and print this image.

This new target sheet is then observed under many different kinds of light. Observations were made for color shifts, colors matching where they shouldn't, and unusually light or dark colors. No fluorescence was observed with these inks. The observations are listed below by categories corresponding to the type of light used.

INKJET RESULTS

spacer
Natural Lights
Type	Light Source	Errors	Anomalies Noted
spacer
0	Sunlight	0	No anomalies noted
spacer
0	Bright Cloudy	0	No anomalies noted
spacer
0	Northern Sky	0	No anomalies noted
spacer
0	Overcast Sky	0	No anomalies noted
spacer
0	Low Sun through Thin Cloud	0	No anomalies noted
spacer
0	Green Grove (Surrounded by foliage)	0	No anomalies noted
spacer
Incandescent & Halogen Lights
Type	Light Source	Errors	Anomalies Noted
spacer
I	Incandescent	7	Blues are subdued
spacer
I	Halogen	5	Blues somewhat subdued
spacer
Old Fluorescent Tubes
Type	Light Source	Errors	Anomalies Noted
spacer
II	Old Daylight Fluorescent	0	No anomalies noted
spacer
II	Old Cool White Fluorescent	0	No anomalies noted
spacer
II	Old Warm White Fluorescent	4	Blues somewhat subdued
spacer
Compact Fluorescent Lights (CFL)
Type	Light Source	Errors	Anomalies Noted
spacer
V	Daylight CFL	0	No anomalies noted
spacer
V	Daylight CFL Filter	0	No anomalies noted
spacer
VI	Daylight CFL Phosphor	0	No anomalies noted
spacer
V	"Full-Spectrum" CFL	0	No anomalies noted
spacer
V	Soft White CFL	15	Turquoise thru violet darker
spacer
Light Emitting Diodes (LED)
Type	Light Source	Errors	Anomalies Noted
spacer
III	Daylight LED	0	No anomalies noted
spacer
III	Daylight LED Filter	0	No anomalies noted
spacer
III	Soft White LED	5	Blues somewhat subdued
spacer
Special Combinations
Type	Light Source	Errors	Anomalies Noted
spacer
I (III, VII)	Special Full Spectrum Set*	0	No anomalies noted (comparison standard)
spacer
III, V, VII	Full Spectrum Set* + Daylight CFL	0	No anomalies noted
spacer
III, VII	Daylight LED and Blue CFL	7	Reds somewhat subdued
spacer
III, VII	Soft White LED and Blue CFL	0	No anomalies noted
spacer
I, III, VII	Full Spectrum Set* + Incandescent	0	No anomalies noted
spacer
I, VII	Incandescent + Blue CFL	0	No anomalies noted
spacer
III	Mix of Daylight and Cool White LEDs†	0	No anomalies noted
spacer
III, V	Mix of Daylight LED and Daylight CFL	0	No anomalies noted
spacer
V	Soft White and Daylight CFL	0	No anomalies noted

spacer
RGB Sources
Type	Light Source	Errors	Anomalies Noted
spacer
VII	Red, Green, and Blue CFLs	0	No anomalies noted
spacer
VII	RGB color monitor producing white light	0	No anomalies noted
spacer
VII	Blue CFL	56	Only Blue, Cerulean, and Black are correct	All yellows and greens are very dark green
All reds and oranges are black	All other colors are shades of blue
spacer
Metallic Arc Lights
Type	Light Source	Errors	Anomalies Noted
spacer
IV	High Pressure Sodium Vapor	30	Hues from Purple to Vermillion close to Black	Pale Cyan is Lilac
Yellow same as Amber	Chestnut is darker
Hues from Green to Violet are darker	Ochres are greener
Pink is dark	Salmon is darker
Pale Green is dark	White is orangish
spacer
IV	Mercury Vapor	33	Hues from Purple to Vermillion very dark	Chestnut is almost Black
Yellow very close to Amber	Salmon is dark
Hues from Lime to Violet dark	Tan is darker
Cyan darker than Green or Blue	Timberwolf looks reddish
spacer
IV	High Intensity Discharge (HID)	11	Hues from Cerise to Vermillion are dark	Orange Browns darker than normal
Pink looks Orange	Salmon is grayish
Chestnut is dark
spacer

NOTES

* The Full-Spectrum Set is described above.

† This situation had the steel blue appearance of the umbrella with an older Daylight LED bulb. Neither the original bulb nor the replacement bulb caused any anomalies on the inkjet target.

Note that the inkjet target has no anomalies with most light sources. This is because the pigments are tuned to match the primary colors of the human eye. Anomalies show up only where a light source emits primarily spectral bright lines that do not correspond to the visual primary colors. The mercury vapor lamp, with a yellow-orange line, a yellow green line, a blue line, and a violet line, is a primary example of this.

EPILOGUE

The following happened after the initial results were published:

The red CFL in the RGB source was found to be emitting much less light than either the green or the blue CFL. It was replaced with a brighter red CFL from a different manufacturer. The tables were updated, with the results that pertain to only the old red CFL being marked with a ‡ symbol.
Originally, the Red Violet crayon was missing from the box. It was subsequently found, and the results for this crayon have been added to the tables.
Cyan CFLs were substituted for the blue ones in the full spectrum lamp assembly. This filled in the cyan dip better than the blue. It did not alter any of the results.
Attempts were made to photograph the two targets under various lights. The results were totally inconsistent with the results that were expected. For example, the photo with the bluest color tinting was made using the Soft White LED. The author concluded that the automatic color-temperature compensation circuits in the digital camera were fooled by the peaks and dips in the spectra of the various lamps.

INTERPRETING THE RESULTS

Check the numbers in the Errors column above. The lack of quality of a light source is roughly represented by the high number of errors in color perception it produces. The best light sources should produce few or no errors. But using pigments unlike the ones used might alter the results. Each pigment has its own spectral response curve, and can behave very differently under different lights.

Note particularly that the inkjet results are much better under a greater variety of light sources than the wide selection of pigments. This means that the colors produced by CMY technology are compatible with many more light sources than other colorants.

PART II - PRACTICAL IMPLICATIONS

IMPLICATIONS OF THE RESULTS

The following table contains implications and practical applications of the results of these experiments:

Case	Effects of Different Light Sources	Effects of Different Pigments
General	Some light sources affect perceived colors more than others. Continuous spectrum - BEST Continuous with bright lines Spectra with gaps Spectra with bright lines and gaps Bright line spectrum - WORST	Some pigments are less sensitive to light sources than others: Mixing Cyan, Magenta, and Yellow (CMY) - BEST Single pigments used for their own colors Pigments that change hue with concentration Mixing old primaries Red, Yellow, and Blue (RYB) Pigments with complex absorption curves - WORST
	Sources with bright line spectra distort colors, because a color close to a bright line can be changed to the color of the line. The worst such sources are: Mercury vapor Sodium vapor High Intensity Discharge (HID)	CMY Mixtures keep their colors under more light sources because each primary pigment removes parts of the spectrum that stimulate one type of cone cell in the eye: Cyan removes light that stimulates the Red cone. Magenta removes light that stimulates the Green cone. Yellow removes light that stimulates the Blue cone.
	Several sources can be combined to make a nearly flat Full-Spectrum Light Source.	Several sources can be combined to make a nearly flat Full-Spectrum Light Source.
Fine Arts	Full-spectrum lighting works better with a wide range of fine arts pigments and materials than light sources that have gaps or bright lines in their spectra: A flat light source gives accurate color with more pigments than a source with bright lines or gaps in the spectrum. The artist must test his color mixtures under various light sources if he will exhibit the work under those lights. Some artists build their own light sources into the frames, so the colors are right. Test the film and flashgun if you plan to photograph the art.	Colors mixed using CMY pigments are better for fine arts than other pigments are, because they keep their colors under a broader range of light sources: Use of CMY color mixtures is a must of the work will be displayed under many different light sources. Mixtures of the traditional artist primaries (Red, Yellow, and Blue, or RYB) will change color under different light sources. The canvas itself may appear to be different colors under different light sources. Some materials fluoresce under ultraviolet or blue light.
Case	Effects of Different Light Sources	Effects of Different Pigments
Photography:	Different lights affect the way various pigments are photographed: A flat light source gives a more accurate rendering than a source with spectral bright lines or dark gaps. Color balance adjustments are usually different for white and colors then the light source has spectral bright lines or dark gaps. Because the film uses RGB technology, the colors seen in the photographs have some of the same errors the human vision system sees. The xenon flash and the magnesium flashbulb are nearly flat sources for this purpose.	Different pigments have different color accuracy under different lights: Objects made with CMY pigment mixtures give more accurate renderings under different lights than other pigments do. Color balance adjustments are the same for white and for colors when CMY pigment mixtures are in the objects being photographed. CMY works with color photography so well because color photography also uses RGB and CMY in the color photography process. Even the best pigment mixtures don't render correctly with mercury, sodium, or HID lamps.
Stage Lighting:	Full-spectrum stage lighting works better with a wide range of pigments than sources with spectral gaps or bright lines. A flat light source gives more accurate color than a source with bright lines or gaps in the spectrum. Color media often give wrong colors with spectral bright lines or dark gaps. Many of the new sources are not suitable for spotlights because they can't produce a focused beam. Many of the new sources can't be dimmed. The carbon arc has a spectrum close to a continuous one.	Color media, scene paints, fabric dyes, and makeup made with CMY mixtures work better with a wider variety of light sources. Objects made with CMY pigment mixtures give more accurate colors than those made with other pigments. Colors still appear proper even when tinted by the color media in the stage lights. Different sources and pigments can be used to make painted images appear and disappear. Few pigments look right with mercury, sodium, or HID lamps. CMY pigments work better with carbon arc follow spots.
Case	Effects of Different Light Sources	Effects of Different Pigments
Interior Lighting:	Full-spectrum interior lighting works better with various colored walls and objects than sources with spectral gaps or bright lines. A flat light source gives more accurate color than a source with bright lines or gaps in the spectrum. The color of paint for the walls and trim must be evaluated under the light source to be used in the interior space. The colors of most objects can't be changed. Test critical objects under several light sources to choose the best one. Many of the new light sources can't be dimmed.	Walls and objects with CMY pigment mixtures show colors more faithfully work better under a wider variety of light sources. Walls and objects made with mixed CMY pigments give more accurate colors than those made with other pigments. The 12- or 16-pigment mixing systems in paint stores do not have the light source compatibility that CMY mixtures have. The colors of most objects can't be changed. Pick a light source so critical objects look right before choosing paint. Wood, paneling, and stain change color with different lights.
Matching Colors	Anyone who needs to match colors, or make sure a color does not change with lighting, needs a large bank of different light sources to try, one at a time or in combinations, to make sure the colors behave as intended.	Anyone who needs to match colors, or make sure a color does not change with lighting, needs to use CMY pigments. Because they match the response of the human eye, they match under a larger variety of light sources.
Identifying Colors	Anyone who needs to be able to recognize colors, or tell the difference between two colors, needs a flat-spectrum light source. In addition a set of colored light sources or color filters can aid in the discrimination between colors that are close together. Having standard color swatches available will help.	Anyone who needs to be able to identify color codes at a glance needs a set of colors that are easy to tell apart under various lights. Colors going around the color wheel should alternate dark and light, and should be far enough apart. Black, brown, gray, white, silver, and gold are also good colors to use.

PART III - THE THEORY

THEORY BEHIND THE RESULTS

About Primary Colors

Light Sources

Pigments

How colored light stimulates the RGB cones in the human eye:

Color	Red Cone	Green Cone	Blue Cone
Red	Full	Low	None
Orange	Full *	Medium	None
Yellow	Full	Full	Slight
Green	Low	Full *	Low
Cyan	Slight	Full	Full
Blue	Slight	Slight	Full *
Violet	Medium	Slight	Full
Magenta	Full	Slight	Full
White	Full	Full	Full
Gray	Medium	Medium	Medium

* Center of sensitivity band

Other relative strengths provide the tints and shades of each color. Note that all colors stimulate at least two cones, even if minimally.

Mixtures made using the CMY pigments do the following:

Primary	Reflects or Passes	Absorbs
Cyan	green cyan * blue	red orange yellow some violet
Magenta	red blue violet	yellow green * cyan some orange
Yellow	red orange yellow * green	cyan blue violet

* Center of reflection, pass, or absorption band

The dilution or concentration of each pigment determines the amount of absorption of the colors absorbed. A white base is assumed.

Effects of mercury vapor bright lines on pigments:

Pigment Color	Color with Lines: amber lime blue violet	Color with Lines: red amber lime blue violet
red	black	dark red
vermillion	brown	brick red
orange	dark amber	dark orange
amber	yellow	amber
yellow	yellow	yellow
green yellow	yellow	yellow
green	lime	lime
cyan	dark cyan	dark cyan
blue	blue	blue
violet	dark blue	dark blue
magenta	dark blue	dark purple
white	blue-white	bluish white

A bright line can contribute only its own color to the visible result. The result thus consists of a mix of only the reflected portions of the bright lines.

A bright line will pull the perceived color toward its own color.

Mixtures made using the traditional RYB pigments do the following:

Primary	Concentrated Reflects or Passes	Dilute Reflects or Passes	Absorbs
Red	red *	red * some orange some blue violet	some orange yellow green cyan
Yellow	red orange yellow * green	red orange yellow * green	cyan blue violet
Blue	blue *	some red some green cyan blue violet*	red orange yellow some green

* Center of pass band

These create different colors by adjusting the slope of a pigment's response, rather than adjusting the amount of filtering of the center wavelength of each primary color of light. Thus, different light sources affect these slopes differently.

THE CRAYON TRIALS

Using a Crayola® box of 64 crayons to test the effects of different
kinds of lighting on colors perceived by normal human vision

Also testing an alternate target printed on a color printer

SUMMARY OF THE CONCLUSIONS

THE PROBLEM

THE TYPES OF LIGHT SOURCES TESTED

PART I - THE EXPERIMENTS

THE CRAYON PROCEDURE

CRAYON RESULTS

NOTES

THE INKJET PROCEDURE

INKJET RESULTS

NOTES

EPILOGUE

INTERPRETING THE RESULTS

PART II - PRACTICAL IMPLICATIONS

IMPLICATIONS OF THE RESULTS

PART III - THE THEORY

THEORY BEHIND THE RESULTS

THE CRAYON TRIALS

Using a Crayola® box of 64 crayons to test the effects of different kinds of lighting on colors perceived by normal human vision

Also testing an alternate target printed on a color printer

SUMMARY OF THE CONCLUSIONS

THE PROBLEM

THE TYPES OF LIGHT SOURCES TESTED

PART I - THE EXPERIMENTS

THE CRAYON PROCEDURE

CRAYON RESULTS

NOTES

THE INKJET PROCEDURE

INKJET RESULTS

NOTES

EPILOGUE

INTERPRETING THE RESULTS

PART II - PRACTICAL IMPLICATIONS

IMPLICATIONS OF THE RESULTS

PART III - THE THEORY

THEORY BEHIND THE RESULTS

Using a Crayola® box of 64 crayons to test the effects of different
kinds of lighting on colors perceived by normal human vision