Abstract

Thresholds of visual detectability were determined for signals on a modified 7BP7 cathode-ray tube. Thresholds were determined in units of signal voltage for three pip sizes, all relatively small, and for four screen brightnesses at each of several positions from the line of binocular regard to 20 degrees out from it. The purpose was to determine the limits within which chance eccentricity of view could be a factor in radar detection. The range of impairment from zero to twenty degrees of eccentricity was about 17 db of signal voltage. The course of the impairment is probably not quite linear, with the optimal scope brightness (about 0.16 footlambert for this phosphor), but the slope is a function of scope brightness. For very small pips the data show no region of equal visibility, even within the fovea; direct fixation is required for maximal detection. There being no data based on optically precise stimuli available for comparison with the radar thresholds, an estimate was made of the luminances of the pips and their backgrounds. As estimated, the visual threshold probably varies up to one-log unit or greater over a range of 20 degrees of viewing angle, for the optimal scope background.

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  1. Williams, Bartlett, and King, "Visibility on cathode-ray tube screens: screen brightness," J. Psych. 25, 455 (1948).
  2. L. L. Sloan, "Rate of dark adaptation and regional threshold gradient of the dark-adapted eye: physiologic and clinical studies," Am. J. Opthal. 30, 705–720 (1947).
  3. W. J. Crozier, and A. H. Holway, "Theory and measurement of visual mechanisms. I. A visual discriminometer. II. Thresholdstimulus intensity and retinal position," J. Gen. Physiol. 22, 362 (1939).
  4. W. H. Howell, Textbook of Physiology (W. B. Saunders Company, Philadelphia, 1947), see Chapter 23, "Vision," by T. C. Ruch.
  5. S. R. Wallace, Jr., "Intensity discrimination in the peripheralretina," Psych. Bull. 37, 552 (1940).
  6. K. J. W. Craik, and S. J. MacTherson, "The effect of certain operating conditions on the visibility of P.P.I, radar echoes," Med. Res. Council, UAP, Cambridge, England, No. 16, December 3, 1945.
  7. S. B. Williams, and N. R. Bartlett, "Visibility on cathode-raytube screens: problems and methods," J. Psych. 25, 401–417 (1948).
  8. R. M. Hanes, and S. B. Williams, "Visibility on cathode-raytube screens: the effects of light adaptation," T. Opt. Soc. Am. 38, 363–377(1948).
  9. The writer is indebted to Mrs. Beverly Richards and Mr. Hamilton Mowbray for their services as observers.
  10. W. S. Stiles, "The directional sensitivity of the retina and the spectral sensitivities of the rods and cones," Proc. Roy. Soc. London, 127B, 64–105 (1939).
  11. H. R. Blackwell, "Contrast thresholds of the human eye," T. Opt. Soc. Am. 36, 624–643 (1946).

1948 (3)

Williams, Bartlett, and King, "Visibility on cathode-ray tube screens: screen brightness," J. Psych. 25, 455 (1948).

S. B. Williams, and N. R. Bartlett, "Visibility on cathode-raytube screens: problems and methods," J. Psych. 25, 401–417 (1948).

R. M. Hanes, and S. B. Williams, "Visibility on cathode-raytube screens: the effects of light adaptation," T. Opt. Soc. Am. 38, 363–377(1948).

1947 (1)

L. L. Sloan, "Rate of dark adaptation and regional threshold gradient of the dark-adapted eye: physiologic and clinical studies," Am. J. Opthal. 30, 705–720 (1947).

1946 (1)

H. R. Blackwell, "Contrast thresholds of the human eye," T. Opt. Soc. Am. 36, 624–643 (1946).

1940 (1)

S. R. Wallace, Jr., "Intensity discrimination in the peripheralretina," Psych. Bull. 37, 552 (1940).

1939 (2)

W. J. Crozier, and A. H. Holway, "Theory and measurement of visual mechanisms. I. A visual discriminometer. II. Thresholdstimulus intensity and retinal position," J. Gen. Physiol. 22, 362 (1939).

W. S. Stiles, "The directional sensitivity of the retina and the spectral sensitivities of the rods and cones," Proc. Roy. Soc. London, 127B, 64–105 (1939).

Bartlett, N. R.

S. B. Williams, and N. R. Bartlett, "Visibility on cathode-raytube screens: problems and methods," J. Psych. 25, 401–417 (1948).

Blackwell, H. R.

H. R. Blackwell, "Contrast thresholds of the human eye," T. Opt. Soc. Am. 36, 624–643 (1946).

Craik, K. J. W.

K. J. W. Craik, and S. J. MacTherson, "The effect of certain operating conditions on the visibility of P.P.I, radar echoes," Med. Res. Council, UAP, Cambridge, England, No. 16, December 3, 1945.

Crozier, W. J.

W. J. Crozier, and A. H. Holway, "Theory and measurement of visual mechanisms. I. A visual discriminometer. II. Thresholdstimulus intensity and retinal position," J. Gen. Physiol. 22, 362 (1939).

Hanes, R. M.

R. M. Hanes, and S. B. Williams, "Visibility on cathode-raytube screens: the effects of light adaptation," T. Opt. Soc. Am. 38, 363–377(1948).

Holway, A. H.

W. J. Crozier, and A. H. Holway, "Theory and measurement of visual mechanisms. I. A visual discriminometer. II. Thresholdstimulus intensity and retinal position," J. Gen. Physiol. 22, 362 (1939).

Howell, W. H.

W. H. Howell, Textbook of Physiology (W. B. Saunders Company, Philadelphia, 1947), see Chapter 23, "Vision," by T. C. Ruch.

MacTherson, S. J.

K. J. W. Craik, and S. J. MacTherson, "The effect of certain operating conditions on the visibility of P.P.I, radar echoes," Med. Res. Council, UAP, Cambridge, England, No. 16, December 3, 1945.

Mowbray, Hamilton

The writer is indebted to Mrs. Beverly Richards and Mr. Hamilton Mowbray for their services as observers.

Richards, Beverly

The writer is indebted to Mrs. Beverly Richards and Mr. Hamilton Mowbray for their services as observers.

Sloan, L. L.

L. L. Sloan, "Rate of dark adaptation and regional threshold gradient of the dark-adapted eye: physiologic and clinical studies," Am. J. Opthal. 30, 705–720 (1947).

Stiles, W. S.

W. S. Stiles, "The directional sensitivity of the retina and the spectral sensitivities of the rods and cones," Proc. Roy. Soc. London, 127B, 64–105 (1939).

Wallace, Jr., S. R.

S. R. Wallace, Jr., "Intensity discrimination in the peripheralretina," Psych. Bull. 37, 552 (1940).

Williams, S. B.

R. M. Hanes, and S. B. Williams, "Visibility on cathode-raytube screens: the effects of light adaptation," T. Opt. Soc. Am. 38, 363–377(1948).

S. B. Williams, and N. R. Bartlett, "Visibility on cathode-raytube screens: problems and methods," J. Psych. 25, 401–417 (1948).

Am. J. Opthal. (1)

L. L. Sloan, "Rate of dark adaptation and regional threshold gradient of the dark-adapted eye: physiologic and clinical studies," Am. J. Opthal. 30, 705–720 (1947).

J. Gen. Physiol. (1)

W. J. Crozier, and A. H. Holway, "Theory and measurement of visual mechanisms. I. A visual discriminometer. II. Thresholdstimulus intensity and retinal position," J. Gen. Physiol. 22, 362 (1939).

J. Psych. (2)

S. B. Williams, and N. R. Bartlett, "Visibility on cathode-raytube screens: problems and methods," J. Psych. 25, 401–417 (1948).

Williams, Bartlett, and King, "Visibility on cathode-ray tube screens: screen brightness," J. Psych. 25, 455 (1948).

Proc. Roy. Soc. London (1)

W. S. Stiles, "The directional sensitivity of the retina and the spectral sensitivities of the rods and cones," Proc. Roy. Soc. London, 127B, 64–105 (1939).

Psych. Bull. (1)

S. R. Wallace, Jr., "Intensity discrimination in the peripheralretina," Psych. Bull. 37, 552 (1940).

T. Opt. Soc. Am. (2)

H. R. Blackwell, "Contrast thresholds of the human eye," T. Opt. Soc. Am. 36, 624–643 (1946).

R. M. Hanes, and S. B. Williams, "Visibility on cathode-raytube screens: the effects of light adaptation," T. Opt. Soc. Am. 38, 363–377(1948).

Other (3)

The writer is indebted to Mrs. Beverly Richards and Mr. Hamilton Mowbray for their services as observers.

K. J. W. Craik, and S. J. MacTherson, "The effect of certain operating conditions on the visibility of P.P.I, radar echoes," Med. Res. Council, UAP, Cambridge, England, No. 16, December 3, 1945.

W. H. Howell, Textbook of Physiology (W. B. Saunders Company, Philadelphia, 1947), see Chapter 23, "Vision," by T. C. Ruch.

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