Colour vision

by Sir William de Wiveleslie Abney

Measurements of Colour Fields.

Some experiments in the measurement of the colour fields in the horizontal direction with the pure spectrum colours will help to show what importance is to be attached to the luminosity of the colour and the size of the spot of light with which the observations are made. A yellow and a blue of the spectrum were taken of such hues that when mixed they formed a patch of white light similar to the electric light. Their luminosities were measured, and the yellow found to be 1·6 of the light of an amyl-acetate lamp or 1·28 standard candles; the blue was 1/24 of this luminosity. The fields for these two colours were measured by automatically throwing spots of each colour separately on a white card which moved round a centre over which the eye was placed. The light was subsequently diminished to ½, ¼, and ⅛ of the above values, and readings again made. The following results were obtained with a spot of ·7 inch diameter:—

Light	Yellow.		Blue.
	Nasal side.	Temporal side.	Nasal side.	Temporal side.
Full	33°	45°	35°	45°
½	24°	36°	26°	38°
¼	18°	24°	22°	32°
⅛	11°	15°	19°	30°

With a spot of ·3 inch diameter the following were obtained:—

Full	24°	32°	21°	27°
½	17°	28°	16°	22°
¼	13°	16°	14°	20°
⅛	8°	10°	13°	16°

It will be evident how the field contracts as the light is diminished in brightness, and also that the blue field does not diminish equally with the yellow field, but is more persistent. Again, it will be noticed that the luminosity of the blue, for the same extent of field to be covered, has to be much lower than for the yellow.

The diminished area of the spot of light also diminishes the field, and the same order of diminution of field is obtained as with the larger spot.

Another set of experiments, made with the same aperture of slit passed through the spectrum, and the field taken at different points, give the following results:—

Spectrum scale. (See [Fig. 41], [Page 210].	Nasal side.	Temporal side.
58·6	18°	35°
54·6	27°	46°
50·6	33°	47°
46·6	25°	30°
42·6	21°	21°
38·6	17°	17°
34·6	22°	30°
30·6	25°	33°
26·6	33°	40°
22·6	37°	44°
18·6	28°	40°
14·6	22°	34°
8·6	20°	30°

Here we see that although the luminosity of the colour spots varies at the spectrum luminosity, the fields do not vary proportionally; when the luminosities of the green, yellow and red are made equal, the fields become nearly equal on the nasal side. The field for the blue, however, then becomes vastly larger than that for the others, showing a peculiarity which is very remarkable.

Fig. 41.

Spectrum Scale.

Recently published experiments on colour fields have been so largely based on the exigencies of the Hering theory, that it is somewhat difficult to decide their significance from any other aspect.

Table I.—Luminosity Curves for the Normal Eye (see [Fig. 20]).

I.	II.	III.	IV.	V.
Scale number.	Wave- length.	Outside yellow spot.	Yellow spot.	Fovea centralis.
64	7217
63	7082	..	1
62	6957	1	2	2
61	6839	2	4	4
60	6728	3·5	7	8
59	6621	7·5	12·5	15·5
58	6520	12·5	21	24
57	6423	19	33	37·5
56	6330	27·5	50	60
55	6242	35	65	77
54	6152	43	80	90
53	6074	52·5	90	97
52	5996	61·0	96	100
51	5919	71·0	99	100
50	5850	79·0	100	98
49	5783	84	99	95
48	5720	85	97	90
47	5658	83·5	92·5	85
46	5596	81·0	87	79
45	5538	77·0	81	72·5
44	5481	72.5	75	66
43	5427	68·0	69	59
42	5373	62·5	62·5	51
41	5321	57	57	45
40	5270	52	50	40
39	5221	46	42·5	32
38	5172	41·5	36	27·5
37	5128	37·5	29·5	22·0
36	5085	33·5	24	18
35	5043	30·0	18·2	14
34	5002	26·5	14·2	10
33	4963	24	10·5	8·4
32	4924	21	8·5	6·5
31	4885	18·5	7·0	5·5
30	4848	16·5	5·5	4·0
29	4812	14·5	4·7	3·5
28	4776	13·0	4·0	3·0
27	4742	11·5	3·5	2·0
26	4707	10·5	2·8	2·4
25	4675	9·4	2·3	2·1
24	4639	8·2	1·82	1·9
23	4608	7·3	1·6	1·5
22	4578	6·3	1·4
21	4548	5·7	1·2
20	4517	5·0	1·08	1·0
19	4488	4·5	·94
18	4459	4·0	·86
17	4437	3·6	·78
16	4404	3·1	·70
15	4377	2·7	·62	·62
14	4349	2·3	·56
13	4323	2·1	·50
12	4296	1·9	·45
11	4271	1·65	·40
10	4245	1·4	·34
9	4221	1·2	·30
8	4197	1·0	·26
7	4174	·88	·22
6	4151	·75	·18
5	4131	·63	·16
4	4106	·50	·14

Tables II. and III.—Curves of Luminosity of a Partially Red-Blind and of a Partially Green-Blind Person (see [Fig. 23]).

Scale number.	Wave- length.	Luminosity.
		Red-blind.	Green-blind.
64	7217	0	1
62	6957	1	2
60	6728	2	7
58	6520	6	21
56	6330	12	50
54	6152	26	80
52	5996	49	96
50	5850	70	98
48	5720	77	93
46	5596	77	83
44	5481	70	70
42	5373	61	55
40	5270	47	40
38	5172	34	27
36	5085	23	18
34	5002	14	10
32	4924	8·5	5·5
30	4848	5·5	3·0
28	4776	4·0	2·5
26	4707	2·7	2·0
24	4639	1·8	1·8
22	4578	1·35	1·4
20	4517	1·1	1·1

Table IV.—Luminosity of Spectrum Reduced in Intensity, so that D = 1/132·5 Amyl Lamp 1 Foot Distant (see [Fig. 25]).

Scale number.	Mean reading.	Mean reading, reduced to 100 max.	P. and Q.’s readings, 100 max.	Persistency curve for the centre of the eye.
55·6	·5	·6	2	2
53·6	5·5	7·0	3·6	3·6
51·6	13	16·7	8	8
49·6	23	29·7	22	22
47·6	40	50·0	44	44
45·6	57	71·2	69	69
43·6	70	87·5	93	93
41·6	79	98·7	100	99·5
39·6	78	97·5	99·5	98·5
37·6	74	92·5	96	93
35·6	66	82·5	89	84
33·6	55	68·7	77·5	71
31·6	44·5	55·2	61	53·5
29·6	35	43·7	45·5	36·5
27·6	24	30·0	33·5	24
25·6	17	21·7	25	16
23·6	13	16·7	18	10
21·6	10	12·5	13	8
19·6	8	10·0	9·5	6
13·6	3	3·7	4·2	3
9·6	2	2·5	2·5	2

Table V.—Limit of Colour Vision (see [Fig. 26].).

Scale Number.	Wave- Length.	Mean reading of the colour limit of the spectrum D, being 1 amyl lamp in 1/10000ths.	Luminosity of the ordinary spectrum.	Luminosity of the rays when each colour disappears, each ray having the original luminosity of 1 amyl lamp in 1/100000ths.
61	6839	120	4	48·0
60	6728	67	7	46·9
58	6520	26	21	54·6
56	6330	13	50	65·0
54	6152	9·5	80	76·0
52	5996	9·0	96	86·4
50	5850	9·0	100	90·0
48	5720	9·0	97	87·3
44	5481	9·5	75	71·3
40	5270	10·5	50	52·5
36	5085	12·5	24	30·0
32	4924	18	8·5	15·3
28	4776	32	4·0	12·8
24	4639	55	1·8	12·0
20	4517	90	1·08	9·7
16	4404	160	·70	11·2
12	4296	250	·45	11·0
8	4197	400	·26	10·4
4	4106	700	·14	9·8

Table VI.—Extinction by Central Portion of Normal Eye (see [Fig. 28]).

I.	II.	III.	IV.	V.	VI.
Scale number.	Wave- length.	E. Reduction of original luminosity in millionths to cause extinction.	L. Luminosity of original beam.	(E × L) / 100	Persistency curve 650 / E (Maximum = 100).
64	7217	55,000
63	7082	30,000	1	300·0
62	7957	15,000	2	300·0
61	6839	7500	4	300·0
60	6728	3750	7	262·5
59	6621	1900	12·5	237·5	·34
58	6520	1050	21	220·5	·62
57	6423	650	33	214·5	1·0
56	6333	380	50	190·0	1·71
55	6242	272	65	176·8	2·38
54	6152	196	80	156·0	3·32
53	6074	140	90	126·0	4·64
52	5996	97	96	93·12	6·70
51	5919	57	99	56·43	11·40
50	5850	35	100	35·0	18·6
49	5783	24	99	23·76	27·1
48	5720	17	97	16·49	38·2
47	5658	12·6	92·5	11·65	51·6
46	5596	10·2	87	8·87	63·7
45	5538	8·6	81	6·97	75·6
44	5481	7·4	75	5·55	87·8
43	5427	6·7	69	4·62	97·0
42	5373	6·55	62·5	4·09	99·5
41	5321	6·5	57	3·705	100
40	5270	6·55	50	3·27	98·5
39	5221	6·65	42·5	2·83	97·5
38	5172	6·85	36	2·46	95·0
37	5128	7·2	29·5	2·12	90·0
36	5085	7·6	24	1·82	81·3
35	5043	8·15	18·2	1·48	80·0
34	5002	8·8	14·2	1·25	74·0
33	4963	10·2	10·5	1·07	63·0
32	4924	11·6	8·5	·988	56·0
31	4885	13·6	7·0	·952	47·7
30	4848	16·3	5·5	·896	40·0
29	4812	20·5	4·7	·963	31·7
28	4776	26·0	4·0	1·040	25·0
27	4742	31·0	3·5	1·085	20·9
26	4707	38·5	2·8	1·078	16·9
25	4674	46·0	2·3	1·058	14·1
24	4639	56·0	1·82	1·019	11·6
23	4608	67·0	1·6	1·072	9·7
22	4578	80	1·4	1·120	8·41
21	4548	95	1·2	1·140	7·22
20	4517	107	1·08	1·156	6·1
19	4488	124	·94	1·165	5·23
18	4459	140	·86	1·204	4·64
17	4437	160	·78	1·228	4·1
16	4404	180	·70	1·260	3·60
15	4377	200	·62	1·240	3·25
14	4349	220	·56	1·232	2·95
13	4323	240	·50	1·200	2·7
12	4296	270	·45	1·215	2·4
11	4271	300	·40	1·200	2·18
10	4245	335	·34	1·139	1·94
9	4221	375	·30	1·125	1·73
8	4197	430	·26	1·118	1·51
7	4174	490	·22	1·078	1·32
6	4151	510	·18	·918	1·27
5	4131	640	·16	1·024	1·01
4	4106	750	·14	1·050	0·86

Table VII.—Extinction by Whole Eye (see [Fig. 28]).

I.	II.	III.	IV.	V.	VI.
Scale number.	Wave- length.	E. Reduction of original luminosity in millionths to cause extinction.	L. Luminosity of original beam.	(E × L) / 160	Persistency curve 650 / E (Maximum = 100).
38	5172	6·9	41·5	2·86	94·2
37	5128	7·1	37·5	2·66	91·6
36	5085	7·4	33·5	2·48	87·8
35	5043	7·7	30·0	2·31	84·4
34	5002	8·0	26·5	2·12	81·2
33	4963	8·4	24·0	2·02	77·5
32	4924	8·8	21·0	1·85	73·8
31	4885	9·4	18·5	1·74	69·2
30	4848	10·0	16·5	1·65	65·0
29	4812	10·7	14·5	1·55	60·6
28	4776	11·5	13·0	1·49	56·5
27	4742	13·0	11·5	1·49	50·0
26	4707	14·5	10·5	1·52	44·8
24	4639	18·5	8·2	1·52	34·1
22	4578	23·0	6·3	1·45	28·3
20	4517	30·0	5·0	1·50	21·7
18	4459	39·0	4·0	1·56	16·7
16	4404	51	3·1	1·59	12·3
14	4349	66	2·3	1·52	9·85
12	4296	80	1·9	1·52	8·12
10	4245	110	1·4	1·54	5·91
8	4197	154	1·0	1·54	4·22
6	4151	204	·75	1·54	3·18
4	4106	307	·5	1·54	2·11
2	4063	513	·3	1·54	1·26
0	4020	770	·2	1·54	·84

From 38 to 64 the extinction is the same as with the central part of the eye.

Table VIII.—P.’s Curves[B] (see [Fig. 31]).

I.	II.	III.	IV.	V.	VI.	VII.
Scale number.	Wave- length.	Mean reading of extinction in millionths of original luminosity.	Adopted reading in millionths of original luminosity.	Persistency curve (680 / ad. reading).	P.’s luminosity curve.	Absolute luminosity of extinction. (IV. × VI.) / 14
52	5996	68	68	10	7	34
50	5850	35	35	19·4	19	47·5
48	5720	17	17	40	39	47·3
46	5596	10·2	10	68	65	46·4
45	5538	9·3	9·0	76	76	48·8
44	5481	8·0	8·1	84	90	52·8
42	5373	7·2	7·2	94·5	98	50·3
40	5270	6·7	6·8	100	99	48·1
38	5172	7·2	7·0	97	97·5	48·7
36	5085	8·05	7·7	90	90	49·5
34	5002	8·05	8·4	81	80	47·9
32	4924	9·9	9·8	69	65	45·5
30	4848	13·2	12·5	54	50	44·6
28	4776	13·9	15·0	45·3	36	38·6
27	4742	16·8	17·0	40	31·5	38·2
26	4707	21·6	20·5	32	26·5	38·8
24	4639	30	27	25	19·5	37·6
22	4578	36	35	19	14	35
20	4517	42	45	15·5	10	32·2
16	4404	79	79	8·5	5·5	31·2
10	4245	180	190	3·6	2·5	32·2
6	4151	270	270	2·7

[B] In this and the next two Tables the intensity of the illumination of the D ray before reduction is equal to that of an amyl-acetate lamp at one foot from a screen. The figures in Col. VII. are in millionths of the illumination of an amyl-acetate lamp at one foot distant, every ray being made of that intensity.

Table IX.—H. R.’s Curves (see [Fig. 32]).

I.	II.	III.	IV.	V.	VI.	VII.
Scale number.	Wave- length.	Mean reading of extinction in millionths of original luminosity.	Adopted reading in millionths of original luminosity.	Persistency curve (590 / ad. reading).	Luminosity curve.	Absolute luminosity of extinction (IV. × VI.) / 48
57	6423	1200	1200	·49	5	125
56	6330	900	850	·69	7	124
55	6242	500	550	1·07	10	115
54	6152	250	250	2·36	17	88
53	6074	..	150	3·93	25	78
52	5996	90	90	6·56	35	66
51	5919	60	45	13·1	47	44
50	5850	27	27	21·8	57	32
48	5720	18	15	39·3	66	21
46	5596	10	10	59	69	14
44	5481	9·3	8	73·8	64	11
42	5373	6·5	6·2	95·1	56·5	7
40	5270	5·9	5·9	100	45	5·5
38	5172	6	6	98·3	32	4
36	5085	..	6·6	89·4	20	2·7
35	5043	7	7·2	81·9	16	2·4
34	5002	..	8	73·8	12·5	2·1
32	4924	10	9·6	61·5	8	1·6
30	4848	11·5	12	49·2	6	1·5
28	4776	14·5	14·5	40·7	5	1·5
26	4707	20	17·5	33·7	4	1·5
24	4639	20	22	26·8	3	1·4
22	4578	..	30	19·7	2·4	1·5
18	4459	55	57	10·4	1·3	1·5
14	4349	115	115	5·1	·7	1·7
10	4245	..	160	3·7	·5	1·7
6	4151	200	200	2·9	·4	1·7

Table X.—V. H.’s Curves (see [Fig. 33]).

I.	II.	III.	IV.	V.	VI.	VII.
Scale number.	Wave- length.	Mean reading of extinction in millionths of original luminosity.	Adopted reading in millionths of original luminosity.	Persistency curve (530 / ad. reading).	Luminosity curve.	Absolute luminosity of extinction (IV. × VI.) / 75.
57	6423	500	500	1·1	31	206
56	6330	350	350	1·5	43	200
54	6152	200	180	2·9	61	146·4
52	5996	100	100	5·3	70	93·3
50	5850	40	40	13·3	73	38·9
48	5720	..	25	21·2	69	23
46	5596	10	10	53·0	63	8·4
45	5538	6·5	6·5	81·6	58	5·0
44	5481	6·0	5·7	93	54	4·1
42	5373	5·5	5·3	100	46	3·3
40	5270	5·5	5·4	98·2	36	2·6
38	5172	5·7	5·7	93	24	1·8
36	5085	6·7	6·5	81·6	15	1·3
34	5002	7·0	7·0	75·7	9·5	·89
32	4924	8·5	8·5	62·3	7·0	·79
30	4848	10·7	10·5	50·5	5·0	·70
28	4776	16	16	33·1	3·7	·79
26	4707	..	22·5	23·5	2·7	·81
24	4639	30	31	17·1	1·82	·75
22	4578	42·5	42	12·6	1·4	·78
20	4517	55	55	9·6	1·0	·73
16	4404	105	100	5·3	·7	·93
12	4296	175	170	3·1	·45	1·02
10	4245	200	200	2·7	·34	·91

Table XI.—B. C.’s Curves (see [Fig. 34]).

I.	II.	III.	IV.	V.	VI.
Scale Number.	Wave- length.	Adopted reading in hundred thousandths.	Persistency curve 12,500 readings in V.	Luminosity of original beam.	Absolute luminosity of extinction III. and V.
61	6839	7500	1·6
60	6728	5500	2·3	·5	27·5
59	6622	4000	3·1	1	40
58	6520	2800	4·5	2	56
57	6423	2000	6·2	4	80
56	6330	1500	8·3	6	90
55	6242	1150	10·8	8	92
54	6152	950	13·1	11·5	109·2
53	6074	750	16·6	16	120
52	5996	580	21·6	21·5	125
51	5919	430	29	28·5	122·5
50	5850	350	36	37	129·5
49	5783	275	45·5	47	129·2
48	5720	215	58	60	129
47	5658	170	73·4	76	129·2
46	5596	140	89·3	92	129
45	5538	125	100	98	122·5
44	5481	125	100	100	125
43	5427	130	96·1	97	126
42	5373	150	83	85	127·5
41	5321	180	69·4	65	117
40	5270	215	59	45	96·7
39	5221	250	50	30	75
38	5172	290	43	1·5	723·2
37	5128	335	37	16	53·6
36	5055	380	33	11·5	43·7
34	5002	500	25	7	35
32	4994	650	19	4	26
30	4848	850	14	2·5	23·3
28	4776	1100	11·4	2	22
26	4707	1500	8·3	1·5	22
24	4639	2000	6·2	1	20
22	4578	2700	4·6	5	13·5
18	4459	4750
14	4349	7500
10	4245	11000

Table XII.—M.’s Luminosity Curve compared with the Normal (see [Fig. 30]).

I.	II.	III.	IV.	V.	VI.	VII.
Scale number.	Wave- length.	Mean reading.	Mean reading × 1·8.	Normal luminosity curve, centre of eye.	Difference of last two columns.	Difference × 5·15.
61	6839	2	3·6	4	·4	2·57
59	6621	7	12·6	12·5	-·1	·51
57	6423	18	32·4	33	+·6	3·09
55	6242	36	64·8	65	·2	1·03
53	6074	49	88·2	89·5	1·3	6·71
52	5996	52	95·4	96·5	1·1	5·66
51	5919	54	97·2	99·5	2·3	11·8
50	5850	54	97·2	100	2·8	14·4
49	5782	52·5	94·5	99·5	5·0	25·7
48	5720	50	90	97	7·0	36·0
47	5658	46	82·8	92·5	9·7	49·9
46	5596	41	73·8	87	13·2	68·0
44	5481	32	57·6	75	17·4	89
42	5373	23	43·2	62.5	19·3	99
40	5270	17	30·6	50	19·4	100
38	5172	10	17·5	35·5	18	93
36	5085	4	7·2	24	16·8	86·5
34	5002	1·0	1·8	14·5	12·7	65·5
31	4885	·5	·7	6·5	5·8	37·7
28	4776	0	0	4	4	20·6

Table XIII.—Miss W.’s Curves (see [Fig. 39]).

Scale number.	Wave- length.	Readings.	Extinction in 1/100000.	Persistency curve.
63	7082	0
62	6957	1
60	6728	7
58	6520	18
57	6423	28
56	6330	43
54	6152	76	900	2
52	5996	90	250	7
50	5850	95	130	13·5
48	5720	93	60	29
46	5596	83	34	51
44	5481	71	22	80
42	5321	58	18·5	92
40	5270	46	17·5	100
38	5172	32	18	94
36	5085	21	19·5	90
34	5002	12·5	22	79
32	4924	7	27	65
30	4848	4·5	34	51
28	4776	3·0	40	38·5
25	4675	1·5	60	29
20	4518	0·4	250	7
19	4488	0·0	350	5
16	4404	—	600