Abstract

Based on the optical principle of a slide projector, a visual tristimulus projection colorimeter has been developed. The calorimeter operates with easily interchangeable sets of primary color filters placed in a frame at the objective. The apparatus has proved to be fairly accurate. The reproduction of the color matches as measured by the standard deviation is equal to the visual sensitivity to color differences for each observer. Examples of deviations in the matches among individuals as well as deviations compared with the CIE 1931 Standard Observer are given. These deviations are demonstrated to be solely due to individual differences in the perception of metameric colors. Thus, taking advantage of an objective observation (allowing all adjustments to be judged by a group of impartial observers), the colorimeter provides an excellent aid in the study of discrimination, metamerism, and related effects which are of considerable interest in current research in colorimetry and in the study of color vision tests.

© 1971 Optical Society of America

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References

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  1. S. Rösch, Math. Naturwiss. Unterricht IV, 156 (1951).
  2. L. Bergmann, Der Kleinbildprojektor im naturwissenschaftlichen Unterricht (Fa. Leitz, Wetzlar, 1959).
  3. K. Miescher, Color 5, 46 (1968).
  4. K. Miescher, lecture held at the 1st International AIC Congress, Stockholm, 1969 (to be published in AIC Proceedings, Musterschmidt, 1970).
  5. A. Valberg, Color 5, 46 (1968). The author has also used the modified projectors with success in a guest lecture on colors given at the Norwegian School of Art and Fine Works, Oslo, 1969.
  6. A. Valberg, thesis presented to Mat. Nat. vit. Fakultet, U. of Oslo (Sept.1967).
  7. A. Valberg, lecture held at the 1st International AIC Congress, Stockholm, 1969 (to be published in AIC Proceedings, Musterschmidt, 1970).
  8. A. Valberg, Vision Res. to be published.
    [PubMed]
  9. W. D. Wright, The Measurement of Colour (Hilger & Watts Ltd., London, 1964).
  10. D. L. MacAdam, J. Opt. Soc. Amer. 32, 247 (1942).
    [CrossRef]
  11. W. S. Stiles, G. Wyszecki, J. Opt. Soc. Amer. 52, 58 (1962).
    [CrossRef]

1968

K. Miescher, Color 5, 46 (1968).

A. Valberg, Color 5, 46 (1968). The author has also used the modified projectors with success in a guest lecture on colors given at the Norwegian School of Art and Fine Works, Oslo, 1969.

1962

W. S. Stiles, G. Wyszecki, J. Opt. Soc. Amer. 52, 58 (1962).
[CrossRef]

1951

S. Rösch, Math. Naturwiss. Unterricht IV, 156 (1951).

1942

D. L. MacAdam, J. Opt. Soc. Amer. 32, 247 (1942).
[CrossRef]

Bergmann, L.

L. Bergmann, Der Kleinbildprojektor im naturwissenschaftlichen Unterricht (Fa. Leitz, Wetzlar, 1959).

MacAdam, D. L.

D. L. MacAdam, J. Opt. Soc. Amer. 32, 247 (1942).
[CrossRef]

Miescher, K.

K. Miescher, Color 5, 46 (1968).

K. Miescher, lecture held at the 1st International AIC Congress, Stockholm, 1969 (to be published in AIC Proceedings, Musterschmidt, 1970).

Rösch, S.

S. Rösch, Math. Naturwiss. Unterricht IV, 156 (1951).

Stiles, W. S.

W. S. Stiles, G. Wyszecki, J. Opt. Soc. Amer. 52, 58 (1962).
[CrossRef]

Valberg, A.

A. Valberg, Color 5, 46 (1968). The author has also used the modified projectors with success in a guest lecture on colors given at the Norwegian School of Art and Fine Works, Oslo, 1969.

A. Valberg, thesis presented to Mat. Nat. vit. Fakultet, U. of Oslo (Sept.1967).

A. Valberg, lecture held at the 1st International AIC Congress, Stockholm, 1969 (to be published in AIC Proceedings, Musterschmidt, 1970).

A. Valberg, Vision Res. to be published.
[PubMed]

Wright, W. D.

W. D. Wright, The Measurement of Colour (Hilger & Watts Ltd., London, 1964).

Wyszecki, G.

W. S. Stiles, G. Wyszecki, J. Opt. Soc. Amer. 52, 58 (1962).
[CrossRef]

Color

K. Miescher, Color 5, 46 (1968).

A. Valberg, Color 5, 46 (1968). The author has also used the modified projectors with success in a guest lecture on colors given at the Norwegian School of Art and Fine Works, Oslo, 1969.

J. Opt. Soc. Amer.

D. L. MacAdam, J. Opt. Soc. Amer. 32, 247 (1942).
[CrossRef]

W. S. Stiles, G. Wyszecki, J. Opt. Soc. Amer. 52, 58 (1962).
[CrossRef]

Math. Naturwiss. Unterricht

S. Rösch, Math. Naturwiss. Unterricht IV, 156 (1951).

Other

L. Bergmann, Der Kleinbildprojektor im naturwissenschaftlichen Unterricht (Fa. Leitz, Wetzlar, 1959).

K. Miescher, lecture held at the 1st International AIC Congress, Stockholm, 1969 (to be published in AIC Proceedings, Musterschmidt, 1970).

A. Valberg, thesis presented to Mat. Nat. vit. Fakultet, U. of Oslo (Sept.1967).

A. Valberg, lecture held at the 1st International AIC Congress, Stockholm, 1969 (to be published in AIC Proceedings, Musterschmidt, 1970).

A. Valberg, Vision Res. to be published.
[PubMed]

W. D. Wright, The Measurement of Colour (Hilger & Watts Ltd., London, 1964).

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Figures (9)

Fig. 1
Fig. 1

Top: Schematic representation of the optical system of a slide projector allowing additive proportionate mixtures of two or more filter colors when the filters are adjoining one another before the objective. Bottom: Simplified picture of the light path. Legend: 1: Spherical reflecting mirror. 2: Projection lamp, 500 W, with tungsten filaments. 3: Condensing lens, aspherical, 5 cm × 5 cm. 4: Infrared filter, 5 cm × 5 cm. 5: Hardened ground glass plate, 2 mm thick, fastened to the infrared filter frame. 6: Second condensing lens, f = 200–300 mm. 7: Object plane with slide frame, 5 cm × 5 cm. The desired image form is cut through a black metal plate. 8: Objective lens system. 9: Objective plane OO. Holder with the desired dimensioned square opening and a moveable filter frame. 10: Screen. 11: Field lens. Achromatic lens that can be tipped in and out of the light path.

Fig. 2
Fig. 2

(a) Frontal view of the filter frame and the aperture (ABCD) in the holder 9. (b) The image of (a) formed by the field lens on a screen. Definitions used in the computations.

Fig. 3
Fig. 3

A typical pair of luminous flux distribution (LFD) curves F(X) and F(Y). SX = SY = 14.55 cm.

Fig. 4
Fig. 4

Subdivisions of the aperture (ABCD) with the definitions used in the computations.

Fig. 5
Fig. 5

Triangles representing combinations of three primary colors. The colors PII, W80B, W78AA refer to Fig. 6.

Fig. 6
Fig. 6

Typical example of matches made by four observers with the projection calorimeter. The matched colors PII, W78AA, and W80B are marked by +. Open symbols refer to the 2.2° matches and the same filled symbols to the 3.6° matches. Primaries: (R) = C5A, (G) = C23, (B) = C32 [Fig. 7(a)].

Fig. 7(a) and (b)
Fig. 7(a) and (b)

Spectral transmission curves for two sets of primary filters.

Fig. 8
Fig. 8

Matches made by four observers with the primaries represented in Fig. 7(b). Calculated matched colors for 2° St. Observer are represented by +. Open symbols refer to the average of numerous 2.2° matches and the same filled symbols to the 3.6° matches. For comparison the distribution areas found by Stiles and Wyszecki for five observers matching the colors represented by points (·) on a Donaldson colorimeter are reproduce as rectangles.

Fig. 9
Fig. 9

Two observers’ (G.W. and A. V.) variation in the 3.6° matches of W78AA over a four-month period. Standard deviation in the chromaticity coordinates x and y is shown as ellipses. The nearest MacAdam standard deviation ellipse representing an approximately one third just noticeable difference is shown for comparison.10

Equations (9)

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H X 23 = H max - H X 1 + B X , H Y 12 = H max - H Y 3 + B Y .
H 1 = H X 1 , H 2 = H X 23 · H Y 12 / H max , H 3 = H X 23 · H Y 13 / H max .
H C ( C ) = H 1 ( C 1 ) + H 2 ( C 2 ) + H 3 ( C 3 ) ,
( C ) = l ( C 1 ) + m ( C 2 ) + n ( C 3 ) ,
( C ) = b ( B ) + g ( G ) + r ( R ) .
X i = 400 700 x ¯ λ · S λ · τ λ i β λ , Y i = 400 700 y ¯ λ · S λ · τ λ i β λ , Z i = 400 700 z ¯ λ · S λ · τ λ i β λ ,             i = R , G , B .
X = r X R + g X G + b X B , Y = r Y R + g Y G + b Y B , Z = r Z R + g Z G + b Z B .
x = X / ( X + Y + Z ) , y = Y / ( X + Y + Z ) .
s = [ 1 n - 1 i = 1 n ( p i - p ¯ ) 2 ] 1 2 ,

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