Comparison of Static and Ambulatory Measurements of Illuminance and Spectral Composition That Can Be Used for Assessing Light Exposure in Real Working Environments

Figures & data

Table 1. Weather conditions, positions of the blinds, and artificial lighting conditions at the times of measuring and the total number of static illuminance (Ill) and irradiance (Irr) measurements carried out during the five measurement periods.

	Morning												Afternoon
Period	Weather type				Blind position				Electric lighting		Measurement points		Weather type				Blind position				Electric lighting		Measurement points
	1	2	3	4	1	2	3	4	On	Off	Ill	Irr	1	2	3	4	1	2	3	4	On	Off	Ill	Irr
February/March	6	3	17	6	10	2	3	0	19	0	192	30	10	4	16	2	10	2	3	0	19	1	192	30
April/May	23	4	2	0	15	8	1	3	23	6	204	60	16	9	3	0	14	10	0	3	27	2	204	60
June/July	15	5	9	0	15	7	4	1	27	1	207	60	12	6	11	0	17	7	2	1	28	0	207	60
September/October	8	8	12	0	17	7	2	0	29	1	207	60	1	14	16	0	14	9	2	1	29	1	207	60
December/January	4	7	19	0	19	5	3	1	30	0	208	60	5	6	17	0	18	5	4	1	30	0	208	60

Weather type: 1 = clear, 2 = overcast, 3 = cloudy, 4 = rain cloudy. Blind position: 1 = fully retracted, 2 = down, no tilt, 3 = down, tilted, 4 = fully closed.

Fig. 1. Five examples of office layouts. The plans show where the subjects were seated, positions of computer monitors and luminaires, and locations of the measuring points.

Fig. 2. Drawing showing a typical working position and the normal angle of gaze.

Table 2. Static measurements of horizontal illuminance at the normal working position (E_HN), average illuminance in the room (E_HR), vertical illuminance at the position of the eye (E_VE), and ambulatory recording of illuminance (E_AMB).

		Morning				Afternoon
		EVE	EAMB	EHN	EHR	EVE	EAMB	EHN	EHR
Period		(n = 30)	(n = 15)	(n = 30)	(n = 30)	(n = 30)	(n = 15)	(n = 30)	(n = 30)
February/March	Mean (lx)	340	328	614	495	579	469	600	494
	SD (lx)	259	262	299	179	1464	416	305	219
April/May	Mean (lx)	530	481	750	713	700	976	919	783
	SD (lx)	493	245	422	533	1043	650	804	615
June	Mean (lx)	467	423	743	769	515	782	794	661
	SD (lx)	439	266	424	945	495	700	562	459
September/October	Mean (lx)	367	288	634	532	443	421	1294	901
	SD (lx)	265	139	346	244	588	371	3431	1676
December/January	Mean (lx)	244	127	517	416	202	114	520	400
	SD (lx)	151	69	270	169	100	79	250	142

Table 3. Static measurements of the spectral composition at the position of the eye (IRR_VE) and ambulatory (IRR_AMB) measurements of the spectral composition of the exposing light radiation.

		Morning						Afternoon
		400–550 nm		550–650 nm		650–750 nm		400–550 nm		550–650 nm		650–750 nm
		IRRVE	IRRAMB	IRRVE	IRRAMB	IRRVE	IRRAMB	IRRVE	IRRAMB	IRRVE	IRRAMB	IRRVE	IRRAMB
Period		(n = 30)	(n = 15)	(n = 30)	(n = 15)	(n = 30)	(n = 15)	(n = 30)	(n = 15)	(n = 30)	(n = 15)	(n = 30)	(n = 15)
February/	Mean (%)	67	36	30	21	3	43	63	37	27	21	10	43
March	SD (%)	70	5	9	10	5	10	36	5	8	10	38	11
April/May	Mean (%)	48	36	35	23	17	41	47	36	36	25	17	39
	SD (%)	5	6	5	10	4	7	4	6	5	11	4	8
June	Mean (%)	48	35	35	23	16	42	47	35	36	26	17	39
	SD (%)	5	9	6	15	3	10	5	9	6	15	3	9
September/	Mean (%)	48	32	36	27	16	41	46	33	37	30	17	37
October	SD (%)	5	14	7	30	4	18	4	14	5	29	4	17
December/	Mean (%)	47	30	39	15	14	54	45	32	40	13	15	56
January	SD (%)	6	9	6	17	4	16	4	9	6	16	5	13

Fig. 3. Relative energy distribution for an incandescent lamp, a fluorescent lamp with a correlated color temperature of 3000 K, and daylight, CIE standard illuminant D65.

Table 4. Pearson product-moment correlations (r) between the three parameters included in the static measurement of illuminances in the offices, horizontal illuminance at the normal working position (E_HN), average horizontal illuminance in the room (E_HR), and vertical illuminance at the position of the eye (E_VE).

		Morning			Afternoon
		EVE	EHN	EHR	EVE	EHN	EHR
Period		Pearson’s r(P value)	Pearson’s r (P value)	Pearson’s r (P value)	Pearson’s r(P value)	Pearson’s r(P value)	Pearson’s r(P value)
February/March (n = 30)	EVE	1	0.774 (<0.001)	0.649 (<0.001)	1	0.56 (0.001)	0.754 (<0.001)
	EHN	—	1	0.878 (<0.001)	—	1	0.865 (<0.001)
	EHR	—	—	1	—	—	1
April/May (n = 30)	EVE	1	0.756 (<0.001)	0.205 (0.278)	1	0.714 (<0.001)	0.609 (<0.001)
	EHN	—	1	0.48 (0.007)	—	1	0.941 (<0.001)
	EHR	—	—	1	—	—	1
June/July (n = 30)	EVE	1	0.868 (<0.001)	0.066 (0.272)	1	0.692 (<0.001)	0.439(<0.015)
	EHN	—	1	0.168 (0.374)	—	1	0.883 (<0.001)
	EHR	—	—	1	—	—	1
September/October (n = 30)	EVE	1	0.669 (<0.001)	0.486 (0.006)	1	0.914 (<0.001)	0.888 (<0.001)
	EHN	—	1	0.864 (<0.001)	—	1	0.974 (<0.001)
	EHR	—	—	1	—	—	1
December/January (n = 30)	EVE	1	0.59 (0.021)	0.631 (<0.001)	1	0.6 (<0.001)	0.618 (<0.001)
	EHN	—	1	0.872 (<0.001)	—	1	0.813 (<0.001)
	EHR	—	—	1	—	—	1

Table 5. Results from t-tests showing the comparison of means between the ambulatory measurements of illuminance (E_AMB) and the static measurements of illuminance at the position of the eye (E_VE), horizontally at the normal working position (E_HN), and average illuminance in the room (E_HR).

		Morning			Afternoon
	P value			P value
	EVE versus EAMB	EHN versus EAMB	EHR versus EAMB	EVE versus EAMB	EHN versus EAMB	EHR versus EAMB
February/March (n = 15)	0.692	0.01	0.036	0.315	0.152	0.516
April/May (n = 15)	0.686	0.002	0.056	0.043	0.993	0.684
June (n = 15)	0.862	0.004	0.017	0.141	0.745	0.987
September/October (n = 15)	0.092	<0.001	<0.001	0.706	0.022	0.098
December/January (n = 15)	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001