Abstract

ABSTRACT

Description of an assembly of apparatus consisting of a “monochromatic colorimeter” (previously so called) and complete accessory apparatus for the determination of dominant wave-length, purity and transmission or reflection for white light under definitely specified conditions.

The apparatus is described as it has been actually used at the Bureau of Standards since March 1923.

Salient features of the apparatus and its use are:

  • (1) The use of a specified artificial white light, field illumination being from incandescent filament lamps.
  • (2) The diffusion sphere for the diffuse illumination of samples to be examined by reflection.
  • (3) The convenient arrangement for handling samples to be examined in either transmitted or reflected light.
  • (4) The convenient arrangement for the simultaneous adjustment of dominant wave-length, purity and brightness in the mixture field to match the juxtaposed sample field.
  • (5) The analysis of the mixture of homogeneous and white light by a substitution flicker method.

Details of design of the apparatus, explicit directions for its use and data on its performance as regards precision and accuracy, including extensive tests of the additivity of homogeneous and white brightnesses, are given. These data support the theorem that brightnesses due respectively to homogeneous and heterogeneous stimuli are strictly additive.

© 1924 Optical Society of America

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References

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  1. “Color” is understood as “sensation.” See “Report of Colorimetry Committee,” J. O. S. A. & R. S. I. 6, pp. 531–534; 1922.
  2. Grassmann: Pogg. Ann.,  89, p. 70; May1853, (or Grassmann’s “Math. and Phy. Werke,” 2, part 2, p. 162). Popular expositions may be found in Rood’s, “Modern Chromatics,” Abney’s “Colour Measurement and Mixture” and Luckiesh’s “Color and its Applications.”
  3. “White light” is not at present particularly well defined. Tentatively it may be regarded as heterogeneous light having the spectral distribution of sunlight or of a complete radiator (“black-body”) at a temperature of about 5000° or 6000° absolute. Cf. H. E. Ives, Trans. I. E. S. 5, pp. 196-198; 1910. Priest, B. S. Sci. Pap.,  417. Troland, J. O. S. A. & R. S. I. 6, pp. 557–564, 1922.
  4. Cf. “Report of Colorimetry Committee,” J. O. S. A. & R. S. I. 6, pp. 534–535; 1922.
  5. These definitions should be supplemented by the following statements:—(1)The values of Λ, p, and i as well as Tw or Rw found are subject to a “personal equation” of the observer.2The determination of p(and consequently i) as well as Rw or Tw in general must be predicated upon an assumed method of measuring relative field brightness for colors of different quality.With the first of these facts we shall not deal in the present paper. The second will be considered below.
  6. Quality is that aspect of color determined by hue and saturation.
  7. Abney: “Colour Measurement and Mixture.” London, 1891, particularly Chap. 13. Nutting: “A new precision colorimeter,” B. S. Bull. 9, pp. 1–5; 1913. U. S. Patent No. 1.026,878; May21, 1912. Luckiesh: “Color and its Applications,” 2nd Ed. 1921, pp. 99-101.H. E. Ives: J. O. S. A. & R. S. I. 7, p. 291; 1923.Adam Hilger, Ltd., London, Advertising Circular, entitled, “The Nutting Colorimeter.”
    [CrossRef]
  8. Arrangements to use an illuminated surrounding field have also been made; but, to date, very little use has been made of it. It will probably prove a desirable feature. Larger field sizes are also possible in the present apparatus. The effect of selective reflection of the silver strip is eliminated by the experimental procedure (vide infra).
  9. The transmission of fine ground glass is selective with respect to wave-length.
  10. Pending further quantitative investigation of absolute selective reflection and the establishment of a better standard, a magnesium carbonate block which is apparently“white” is being used tentatively.
  11. H. E. Ives: Jour. Frank. Inst.,  177, pp. 471-499; 1914.E. J. Brady: Trans. I. E. S. 9, pp. 937-952; 1914. The author is greatly indebted to Mr. Norman Macbeth, President of the Macbeth Daylighting Co., for supplying this glass which could not be obtained commercially.
    [CrossRef]
  12. Priest: “Colorimetry and Photometry of Daylight and Incandescent Illuminants,” J. O. S. A. and R. S. I., Dec.1923.
    [CrossRef]
  13. It is planned to later use a rotatory dispersion filter directly in the colorimeter and so eliminate the use of the blue glass filters. Cf. Priest: Phy. Rev. (2)  11, p. 502; 1918. The fact that the spectral distribution of energy in the Ives-Brady or other blue filter white light is not a close approximation to a Planckian distribution, altho competent to evoke the same color, raises the question of the propriety of using it for a standard of general validity.
  14. Adam Hilger’s catalog, Fig. D 25; March, 1921.
  15. Actually a number of such settings of current are made and the mean taken as the standard current for sample illumination.
  16. (Cf. III-4 and V-4 below)
  17. The last named adjustment is used only in the initial adjustment of this current to its standard value. The others are all used in the ordinary course of measurement of Λ, p and i.
  18. The author is indebted to Mr. H. B. Brooks and Mr. R. Davis for advice on this method of speed regulation.
  19. An adapter cap fitting over the slit is provided to hold the ocular.
  20. In practice, it may be necessary to make the adjustments of the grating for approximate wave-length reading and the adjustments for the field illumination alternately until both are satisfactory.
  21. The shunt should always be set so that the sample lamp draws little or no current when the main circuit through the white lamp and the comparison lamp is closed. Neglect of this precaution may result in momentary overload and even burning out of the sample lamp.
  22. If the white component of the mixture field cannot be sufficiently reduced by increasing the distance of the white lamp from the ground glass it may be reduced in large steps by inserting one or more extra plates of similar rough ground glass, using the adjustment of distance as a subsequent fine adjustment.
  23. Jones: Jo. Op. Soc. Am. 1, pp. 63-77; 1917
    [CrossRef]
  24. Computed from measured spectral transmission of the glass and assumed spectral distribution of the lamp.
  25. Measurements by K. S. Gibson and M. Katherine Frehafer, Bureau of Standards.
  26. Cf. H. E. Ives, Phil. Mag.Dec., 1912, pp. 845-853.
    [CrossRef]

1923 (1)

Priest: “Colorimetry and Photometry of Daylight and Incandescent Illuminants,” J. O. S. A. and R. S. I., Dec.1923.
[CrossRef]

1922 (2)

“Color” is understood as “sensation.” See “Report of Colorimetry Committee,” J. O. S. A. & R. S. I. 6, pp. 531–534; 1922.

Cf. “Report of Colorimetry Committee,” J. O. S. A. & R. S. I. 6, pp. 534–535; 1922.

1918 (1)

It is planned to later use a rotatory dispersion filter directly in the colorimeter and so eliminate the use of the blue glass filters. Cf. Priest: Phy. Rev. (2)  11, p. 502; 1918. The fact that the spectral distribution of energy in the Ives-Brady or other blue filter white light is not a close approximation to a Planckian distribution, altho competent to evoke the same color, raises the question of the propriety of using it for a standard of general validity.

1917 (1)

Jones: Jo. Op. Soc. Am. 1, pp. 63-77; 1917
[CrossRef]

1914 (1)

H. E. Ives: Jour. Frank. Inst.,  177, pp. 471-499; 1914.E. J. Brady: Trans. I. E. S. 9, pp. 937-952; 1914. The author is greatly indebted to Mr. Norman Macbeth, President of the Macbeth Daylighting Co., for supplying this glass which could not be obtained commercially.
[CrossRef]

1912 (1)

Cf. H. E. Ives, Phil. Mag.Dec., 1912, pp. 845-853.
[CrossRef]

1910 (1)

“White light” is not at present particularly well defined. Tentatively it may be regarded as heterogeneous light having the spectral distribution of sunlight or of a complete radiator (“black-body”) at a temperature of about 5000° or 6000° absolute. Cf. H. E. Ives, Trans. I. E. S. 5, pp. 196-198; 1910. Priest, B. S. Sci. Pap.,  417. Troland, J. O. S. A. & R. S. I. 6, pp. 557–564, 1922.

1853 (1)

Grassmann: Pogg. Ann.,  89, p. 70; May1853, (or Grassmann’s “Math. and Phy. Werke,” 2, part 2, p. 162). Popular expositions may be found in Rood’s, “Modern Chromatics,” Abney’s “Colour Measurement and Mixture” and Luckiesh’s “Color and its Applications.”

Abney,

Abney: “Colour Measurement and Mixture.” London, 1891, particularly Chap. 13. Nutting: “A new precision colorimeter,” B. S. Bull. 9, pp. 1–5; 1913. U. S. Patent No. 1.026,878; May21, 1912. Luckiesh: “Color and its Applications,” 2nd Ed. 1921, pp. 99-101.H. E. Ives: J. O. S. A. & R. S. I. 7, p. 291; 1923.Adam Hilger, Ltd., London, Advertising Circular, entitled, “The Nutting Colorimeter.”
[CrossRef]

Grassmann,

Grassmann: Pogg. Ann.,  89, p. 70; May1853, (or Grassmann’s “Math. and Phy. Werke,” 2, part 2, p. 162). Popular expositions may be found in Rood’s, “Modern Chromatics,” Abney’s “Colour Measurement and Mixture” and Luckiesh’s “Color and its Applications.”

Ives, H. E.

H. E. Ives: Jour. Frank. Inst.,  177, pp. 471-499; 1914.E. J. Brady: Trans. I. E. S. 9, pp. 937-952; 1914. The author is greatly indebted to Mr. Norman Macbeth, President of the Macbeth Daylighting Co., for supplying this glass which could not be obtained commercially.
[CrossRef]

Cf. H. E. Ives, Phil. Mag.Dec., 1912, pp. 845-853.
[CrossRef]

“White light” is not at present particularly well defined. Tentatively it may be regarded as heterogeneous light having the spectral distribution of sunlight or of a complete radiator (“black-body”) at a temperature of about 5000° or 6000° absolute. Cf. H. E. Ives, Trans. I. E. S. 5, pp. 196-198; 1910. Priest, B. S. Sci. Pap.,  417. Troland, J. O. S. A. & R. S. I. 6, pp. 557–564, 1922.

Jones,

Jones: Jo. Op. Soc. Am. 1, pp. 63-77; 1917
[CrossRef]

Priest,

Priest: “Colorimetry and Photometry of Daylight and Incandescent Illuminants,” J. O. S. A. and R. S. I., Dec.1923.
[CrossRef]

It is planned to later use a rotatory dispersion filter directly in the colorimeter and so eliminate the use of the blue glass filters. Cf. Priest: Phy. Rev. (2)  11, p. 502; 1918. The fact that the spectral distribution of energy in the Ives-Brady or other blue filter white light is not a close approximation to a Planckian distribution, altho competent to evoke the same color, raises the question of the propriety of using it for a standard of general validity.

J. O. S. A. & R. S. I. (2)

Cf. “Report of Colorimetry Committee,” J. O. S. A. & R. S. I. 6, pp. 534–535; 1922.

“Color” is understood as “sensation.” See “Report of Colorimetry Committee,” J. O. S. A. & R. S. I. 6, pp. 531–534; 1922.

J. O. S. A. and R. S. I. (1)

Priest: “Colorimetry and Photometry of Daylight and Incandescent Illuminants,” J. O. S. A. and R. S. I., Dec.1923.
[CrossRef]

Jo. Op. Soc. Am. (1)

Jones: Jo. Op. Soc. Am. 1, pp. 63-77; 1917
[CrossRef]

Jour. Frank. Inst. (1)

H. E. Ives: Jour. Frank. Inst.,  177, pp. 471-499; 1914.E. J. Brady: Trans. I. E. S. 9, pp. 937-952; 1914. The author is greatly indebted to Mr. Norman Macbeth, President of the Macbeth Daylighting Co., for supplying this glass which could not be obtained commercially.
[CrossRef]

Phil. Mag. (1)

Cf. H. E. Ives, Phil. Mag.Dec., 1912, pp. 845-853.
[CrossRef]

Phy. Rev. (1)

It is planned to later use a rotatory dispersion filter directly in the colorimeter and so eliminate the use of the blue glass filters. Cf. Priest: Phy. Rev. (2)  11, p. 502; 1918. The fact that the spectral distribution of energy in the Ives-Brady or other blue filter white light is not a close approximation to a Planckian distribution, altho competent to evoke the same color, raises the question of the propriety of using it for a standard of general validity.

Pogg. Ann. (1)

Grassmann: Pogg. Ann.,  89, p. 70; May1853, (or Grassmann’s “Math. and Phy. Werke,” 2, part 2, p. 162). Popular expositions may be found in Rood’s, “Modern Chromatics,” Abney’s “Colour Measurement and Mixture” and Luckiesh’s “Color and its Applications.”

Trans. I. E. S. (1)

“White light” is not at present particularly well defined. Tentatively it may be regarded as heterogeneous light having the spectral distribution of sunlight or of a complete radiator (“black-body”) at a temperature of about 5000° or 6000° absolute. Cf. H. E. Ives, Trans. I. E. S. 5, pp. 196-198; 1910. Priest, B. S. Sci. Pap.,  417. Troland, J. O. S. A. & R. S. I. 6, pp. 557–564, 1922.

Other (17)

Computed from measured spectral transmission of the glass and assumed spectral distribution of the lamp.

Measurements by K. S. Gibson and M. Katherine Frehafer, Bureau of Standards.

These definitions should be supplemented by the following statements:—(1)The values of Λ, p, and i as well as Tw or Rw found are subject to a “personal equation” of the observer.2The determination of p(and consequently i) as well as Rw or Tw in general must be predicated upon an assumed method of measuring relative field brightness for colors of different quality.With the first of these facts we shall not deal in the present paper. The second will be considered below.

Quality is that aspect of color determined by hue and saturation.

Abney: “Colour Measurement and Mixture.” London, 1891, particularly Chap. 13. Nutting: “A new precision colorimeter,” B. S. Bull. 9, pp. 1–5; 1913. U. S. Patent No. 1.026,878; May21, 1912. Luckiesh: “Color and its Applications,” 2nd Ed. 1921, pp. 99-101.H. E. Ives: J. O. S. A. & R. S. I. 7, p. 291; 1923.Adam Hilger, Ltd., London, Advertising Circular, entitled, “The Nutting Colorimeter.”
[CrossRef]

Arrangements to use an illuminated surrounding field have also been made; but, to date, very little use has been made of it. It will probably prove a desirable feature. Larger field sizes are also possible in the present apparatus. The effect of selective reflection of the silver strip is eliminated by the experimental procedure (vide infra).

The transmission of fine ground glass is selective with respect to wave-length.

Pending further quantitative investigation of absolute selective reflection and the establishment of a better standard, a magnesium carbonate block which is apparently“white” is being used tentatively.

Adam Hilger’s catalog, Fig. D 25; March, 1921.

Actually a number of such settings of current are made and the mean taken as the standard current for sample illumination.

(Cf. III-4 and V-4 below)

The last named adjustment is used only in the initial adjustment of this current to its standard value. The others are all used in the ordinary course of measurement of Λ, p and i.

The author is indebted to Mr. H. B. Brooks and Mr. R. Davis for advice on this method of speed regulation.

An adapter cap fitting over the slit is provided to hold the ocular.

In practice, it may be necessary to make the adjustments of the grating for approximate wave-length reading and the adjustments for the field illumination alternately until both are satisfactory.

The shunt should always be set so that the sample lamp draws little or no current when the main circuit through the white lamp and the comparison lamp is closed. Neglect of this precaution may result in momentary overload and even burning out of the sample lamp.

If the white component of the mixture field cannot be sufficiently reduced by increasing the distance of the white lamp from the ground glass it may be reduced in large steps by inserting one or more extra plates of similar rough ground glass, using the adjustment of distance as a subsequent fine adjustment.

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Figures (8)

Fig. 1
Fig. 1

Horizontal Section through the Axes of the Telescope and Collimator.

Fig. 2
Fig. 2

Vertical Section through the Axis of the Telescope.

Fig. 3
Fig. 3

Perspective View of Whole Apparatus. The observer is shown in the process of adjusting the mixture of homogeneous light and white light to match the sample. His right hand is on the wave-length drum of the spectrometer. His left hand is on the cord by which he moves the white lamp. His right foot is on the slide by which he adjusts the current in the spectral lamp. In the flicker analysis his right hand would reach the cord under the auxiliary photometer track.

Fig. 4
Fig. 4

Wiring Diagram of White Lamp, Comparison Lamp and Sample Lamp.

Fig. 5
Fig. 5

Wiring Diagram of the Spectral Lamp. The double throw single pole switch provides for three rough adjustments of current, the fine adjustment in each case being made by either the hand or foot rheostat.

Fig. 6
Fig. 6

Wiring Diagram of the Flicker Disk Motor. The speed may be varied as indicated by movement of slider on either rheostat. The fine adjustment is normally made by movement o slider A after B has been set by trial at about the required speed.

Fig. 7
Fig. 7

Specimen Data Sheet.

Fig. 8
Fig. 8

Ratio of Heterogeneous Light to Total Light Passing the Spectrum Slit.

Tables (2)

Tables Icon

Table 2 Experimental Values of p + i. Each value of p + i is the MEAN from 10 successive measurements of p and i.

Equations (17)

Equations on this page are rendered with MathJax. Learn more.

p is B Λ B x ;
i is B w B x ;
T w is B x B s .
R w is B x B s .
p = ( D Λ + w D Λ ) 2
and i = ( D Λ + w D w ) 2 .
T w = ( D s D x T ) 2
and R w = ( D s D x R ) 2 .
( D f D 0 ) 2
B d B d + Λ
B d B d + Λ = 0.1258 10 × 0.85 ( D d + Λ D d ) 2
p = p m ( 1 I )
B Λ + B w = B m
p + i = 1
p + i = 1
or B w B m + B Λ B m = 1
or B w + B Λ = B m