Light Damage Calculator
Directions:   Input values into yellow field.  Green fields output results.
Version .9 Beta.  Calculators were develped by Scott Rosenfeld and Anna Yuchen Zhou based on data from CIE157:2004, The Control of Damage to Museum Objects by Optical Radiation.
*JND = Just noticiable difference.  See notes below for details.
*For research purposes, follow this advise at your own risk
Calculator #1: Select illuminannce and preservation target to calculate days per year of constant exposure to JND (assumes lights are on for 8 hours a day)
Light Sensitivity of Material;  ISO Blue Wool	High Light Sensitivity						Moderate Light Senstivity						Low Light Sensitivity
	1		2		3		4		5		6		7		8
	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV
Enter amount of light in Lux
Enter preservation goal in years to JND
# of days of exposure per year @ 8 hour days	7.5	5.5	25	15	38	19	125	44	250	67	365	250	365	104	365	214
Calculator #2:  Select illuminance and preservation target to calculate number of minutes of daily exposure to JND, especially useful for ligths with motion sensors.
Light Sensitivity of Material;  ISO Blue Wool	High Light Sensitivity						Moderate Light Senstivity						Low Light Sensitivity
	1		2		3		4		5		6		7		8
	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV
Enter days per week museum is open  (1-7)
Enter amount of light in Lux
Enter preservation goal in years to JND
Hours and minutes of daily exposure	0:23	0:16	0:32	0:19	1:38	0:49	5:28	1:54	16:25	4:22	4:33	0:54	13:41	2:16	24:00	5:28
Calculator #3:  Select Illuminance and minutes of daily exposure to calculate years to JND (assumes 7 days a week of operation).
Light Sensitivity of Material;  ISO Blue Wool	High Light Sensitivity						Moderate Light Senstivity						Low Light Sensitivity
	1		2		3		4		5		6		7		8
	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV	No UV	UV
Enter days per week museum is open  (1-7)
Enter amount of light in Lux
Enter minutes of daily exposure
Years to JND	2.4	1.8	6.8	4.1	20.5	10.3	34.2	12.0	51.3	13.7	684.5	136.9	410.7	68.4	977.8	117.3
Calculator is based on data from CIE157:2004,  The Control of Damage to Museum Objects by Optical Radiation.   The data in this internationaly agreed upon standard was provided by Michalski (1987, 1994, 1997)
Light Sensitivity of Material	ISO Bluewool rating	Megalux hours to JND*  UV Rich	Megalux hours to  JND* No-UV
High Sensitivity	1	0.22	0.3
	2	0.6	1
	3	1.5	3
Medium Sensitivity	4	3.5	10
	5	8	30
	6	20	100
Low Sensitivity	7	50	300
	8	120	1000
Insensitive
Notes to Table
a. Mlx h is the exposure unit megalux hours =1000 kilolux hours
b. A noticeable difference is defined here as Grey Scale 4 (GS4) , the step used in most lightfastness tests as noticeable. It is approximately equal to a colour difference of 1.6 CIELAB units. There are approximately thirty such steps in the transition from a bright colour to white.
c. UV rich refers to a spectrum similar to daylight through glass. This is the spectrum generally used for the lightfastness data used to derive this table. The exposures here are the best fit to data that varies about ± one Blue Wool step.
d. Exposures estimated for UV blocked light source are derived from a study on 400 dyes and the blue wool standards themselves. As such, it is only probable, and probably only for organic colourants. These estimates show minor benefit of UV filtration for high sensitivity colourants, but large improvements for low sensitivity colourants. For conservative estimates, use the UV rich scale.
e. The specific examples are near optimum tint strength unless noted otherwise ("standard depth" for dyes, peak chroma for pigments.) Heavier concentrations of colourant can be less sensitive by up to two Blue Wool steps. The examples are also for unfaded samples. Partly faded samples may or may not show lower sensitivity. Fading prediction is an imprecise science, so the broad categories of this table  are most practical. Accurate predictions can only be made directly on the artifact in question, or on samples known to be identical. Several researchers are developing microspot tests in Canada, the UK, and the USA.
f. "Insensitive" to light does not mean guaranteed colour life. Many colourants in this group are sensitive to pollution. Many organic media will chalk or yellow or both if any UV is present.
g. The particular paint medium makes only small differences to fading rate, it is the colourant that matters in fading, not whether it is oil, or tempera, or watercolour, or acrylic. Media does, however, make large differences to rate of discolouration from pollutants such as ozone and hydrogen sulphide.
Modern pigments offer artists a full palette of colours that has been developed to have high resistance to the effects of light exposure, and pigments that are rated ASTM D4303 Category 1, or Winsor and Newton AA, are all in the insensitive or low sensitivity categories of light-fastness. However, in the past, artists have used many pigments that are much more responsive to light exposure, and Table 3.3 shows examples of these.
Furthermore, the light-fastness of a pigment may be substantially affected by how it is applied by the artist. Indigo on wool is a low sensitivity material (ISO 7), and there are many examples in museums of woollen tapestries where indigo is the only pigment that is not seriously faded. However, on paper, cotton or silk, indigo becomes a high sensitivity material (ISO 3) and must be treated with great care if its rich blue hue has not already been faded.