Modeling spectral sensitivity at low light levels based on mesopic visual performance

Figures & data

Figure 1 Contrasts of a small flat target (20 cm × 20 cm, p = 0.2) and a pedestrian (p = 0.16) when located at varying positions on the road and the roadside. The results represent two different road lighting conditions measured in dry weather conditions at Ring Road III Vantaa, Finland. The road surface was illuminated by 250 W high pressure sodium lamps with a pole spacing of 55 m. The target contrasts vary between C = −0.88–0.72.

Table 1 a)The values of x given by the modified MOVE-model as a function of photopic luminance and S/P-ratio. b) The values of L_mes given by the modified MOVE-model as a function of photopic luminance and S/P-ratio

a							b
x	Photopic luminance cd/m^2						Lmes	Photopic luminance cd/m^2
S/P	0.01	0.03	0.1	0.3	1	3	S/P	0.01	0.03	0.1	0.3	1	3
0.25		0.1542	0.3830	0.5644	0.7538	0.9225	0.25	0.0025	0.0145	0.0705	0.2467	0.9130	2.9265
0.35		0.1804	0.3920	0.5688	0.7558	0.9230	0.35	0.0035	0.0174	0.0750	0.2545	0.9253	2.9367
0.45	0.0000	0.1992	0.4000	0.5730	0.7576	0.9235	0.45	0.0045	0.0198	0.0793	0.2620	0.9373	2.9468
0.55	0.0190	0.2140	0.4073	0.5770	0.7594	0.9240	0.55	0.0057	0.0220	0.0834	0.2693	0.9492	2.9568
0.65	0.0459	0.2265	0.4139	0.5808	0.7612	0.9245	0.65	0.0069	0.0239	0.0873	0.2764	0.9608	2.9666
0.75	0.0655	0.2373	0.4201	0.5844	0.7629	0.9249	0.75	0.0079	0.0258	0.0911	0.2833	0.9722	2.9763
0.85	0.0812	0.2468	0.4258	0.5878	0.7646	0.9254	0.85	0.0088	0.0275	0.0947	0.2901	0.9835	2.9859
0.95	0.0943	0.2553	0.4311	0.5911	0.7662	0.9258	0.95	0.0096	0.0292	0.0983	0.2967	0.9945	2.9953
1.05	0.1057	0.2631	0.4361	0.5942	0.7678	0.9263	1.05	0.0104	0.0308	0.1017	0.3032	1.0054	3.0046
1.15	0.1157	0.2702	0.4408	0.5972	0.7693	0.9267	1.15	0.0111	0.0323	0.1051	0.3096	1.0161	3.0139
1.25	0.1247	0.2767	0.4452	0.6001	0.7708	0.9272	1.25	0.0118	0.0338	0.1083	0.3158	1.0267	3.0230
1.35	0.1329	0.2828	0.4494	0.6029	0.7723	0.9276	1.35	0.0125	0.0353	0.1115	0.3220	1.0371	3.0319
1.45	0.1404	0.2885	0.4534	0.6056	0.7737	0.9280	1.45	0.0132	0.0367	0.1147	0.3280	1.0473	3.0408
1.55	0.1473	0.2939	0.4573	0.6082	0.7751	0.9284	1.55	0.0138	0.0381	0.1178	0.3339	1.0575	3.0496
1.65	0.1538	0.2990	0.4609	0.6107	0.7764	0.9289	1.65	0.0145	0.0395	0.1208	0.3398	1.0674	3.0582
1.75	0.1598	0.3038	0.4645	0.6131	0.7778	0.9293	1.75	0.0151	0.0408	0.1238	0.3455	1.0773	3.0668
1.85	0.1654	0.3083	0.4678	0.6155	0.7791	0.9297	1.85	0.0157	0.0421	0.1267	0.3512	1.0870	3.0753
1.95	0.1708	0.3126	0.4711	0.6178	0.7803	0.9301	1.95	0.0163	0.0434	0.1295	0.3568	1.0966	3.0836
2.05	0.1758	0.3168	0.4742	0.6200	0.7816	0.9304	2.05	0.0169	0.0446	0.1324	0.3623	1.1060	3.0919
2.15	0.1806	0.3207	0.4772	0.6221	0.7828	0.9308	2.15	0.0174	0.0459	0.1352	0.3677	1.1154	3.1001
2.25	0.1852	0.3245	0.4801	0.6242	0.7840	0.9312	2.25	0.0180	0.0471	0.1379	0.3731	1.1246	3.1082
2.35	0.1895	0.3282	0.4830	0.6263	0.7852	0.9316	2.35	0.0185	0.0483	0.1406	0.3784	1.1338	3.1162
2.45	0.1937	0.3317	0.4857	0.6283	0.7863	0.9319	2.45	0.0191	0.0495	0.1433	0.3836	1.1428	3.1241
2.55	0.1977	0.3351	0.4883	0.6302	0.7875	0.9323	2.55	0.0196	0.0506	0.1459	0.3888	1.1517	3.1319
2.65	0.2015	0.3383	0.4909	0.6321	0.7886	0.9327	2.65	0.0201	0.0518	0.1485	0.3939	1.1605	3.1396
2.75	0.2052	0.3415	0.4934	0.6339	0.7896	0.9330	2.75	0.0207	0.0529	0.1511	0.3989	1.1693	3.1473

Figure 2 a) Coefficients x of MOVE- and modified MOVE-model, and coefficient X of X-model as a function of photopic luminance for HPS (S/P = 0.65) and MH (S/P = 2.35) lamps. b) The ratio of mesopic luminance (calculated using the MOVE-, modified MOVE-, and X-models) to photopic luminance as a function of photopic luminance for HPS (S/P = 0.65) and MH (S/P = 2.35) lamps.

Table 2 The experimental setups and measurement parameters of the three independent visual performance datasets

	L-LAB	UP	HUT
Method	Detection threshold	Detection threshold	Reaction time
Background luminance	0.01, 0.07, 0.7 cd/m^2	0.5 cd/m^2	0.1, 0.3, 1, 3 cd/m^2
Background color	Uniform grey, S/P ≈ 2.8	White, S/P ≈ 2.05	White, S/P ≈ 1.86
Target eccentricity	2°, 6°, 10°, 14°	20°	10°
Target colors	blue, green, grey, red	from 410 to 680 nm, 10 nm steps	blue, cyan, green, amber, red
Target size	0.7°	2°	0.29°
Subjects	40	1 (4 repetitions)	5

Figure 3 Mesopic contrast thresholds of L-LAB detection threshold data (Raphael and Leibenger 2007) as a function of target color at an eccentricity of a) 6°, b) 10°, c) 14°.

Figure 4 The mesopic contrast threshold of UP detection threshold data (Vas and Bodrogi 2007) as a function of target peak wavelength.

Figure 5 The mesopic contrasts of HUT reaction time data (Orreveteläinen 2005) that produce common reaction times as a function of dominant wavelength of target colors at background luminance level of a) 0.1 cd/m², b) 0.3 cd/m², c) 1 cd/m², d) 3 cd/m².

Table 3 The standard deviations between the mesopic contrasts calculated using the MOVE-, modified MOVE-, and X-models

			MOVE-model	X-model	modified MOVE- model
	0.01 cd/m^2	2°	0.1738	0.2076	0.1557
		6°	0.0482	0.0758	0.0317
		10°	0.0159	0.0553	0.0108
		14°	0.0115	0.0877	0.0299
L-LAB Detection threshold	0.07 cd/m^2	2°	0.0509	0.0669	0.0445
		6°	0.0238	0.0361	0.0186
		10°	0.0148	0.0282	0.0110
		14°	0.0110	0.0338	0.0124
	0.7 cd/m^2	2°	0.0117	0.0105	0.0090
		6°	0.0114	0.0154	0.0090
		10°	0.0101	0.0217	0.0112
		14°	0.0140	0.0330	0.0156
UP Detection threshold	0.5 cd/m^2	20°	0.0078	0.0120	0.0085
HUT Reaction time	0.1 cd/m^2	10°	0.0910	0.2127	0.0885
	0.3 cd/m^2	10°	0.0360	0.0301	0.0335
	1 cd/m^2	10°	0.0261	0.1286	0.0386
	3 cd/m^2	10°	0.0314	0.0861	0.0626

RaphaelSLeibengerM2007Models of mesopic photometry applied to the contrast threshold of peripheral and foveal objectsProceedings of the 26th session of the CIE – Beijing1D1-3841Vienna: AustriaCommission Internationale de’Éclairage

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VasZBodrogiP2007Additivity of mesopic photometryProc ISAL2007TU DarmstadtGermany [in press]

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OrreveteläinenP2005Models for spectral luminous efficiency in peripheral vision at mesopic and low photopic luminance levelsPhD dissertationEspooHelsinki University of Technology, Lighting Laboratory

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