A Theory of Visual Intensity Discrimination

Hecht, Selig

doi:10.1085/jgp.18.5.767

Cited by 86 publications

(40 citation statements)

References 18 publications

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“…2 and 3. This is the equation which originally (Hecht, 1935) was found to fit Blanchard's data, those of Steinhardt, of Koenig and Brodhun, and has since been found to describe the more recent data of Smith (1936) and of Graham and Kemp (1938). Its agreement with the present measurements is obvious.…”

Section: Photochemical Theorysupporting

confidence: 81%

“…Fig. 7 in Hecht, 1935). The data as a whole show that the extent of the low intensity section steadily increases as the spectrum goes from red to blue, and this is in conformity with the Duplicity theory as implemented by the spectrum sensibility curves of rods and cones.…”

Section: O I --Photonssupporting

confidence: 78%

“…In addition to their relation to the Duplicity theory, these measurements, in their quantitative implications, are consonant with the theory developed for intensity discrimination in vision and photoreception (Hecht, 1935). Essentially, this theory supposes that in order to discriminate between an intensity I, and another just perceptibly brighter intensity, I + A[, a constant increment in the photochemical decomposition must take place in a given time when the photosensory system in the receptor is exposed to the added intensity AI.…”

Section: Photochemical Theorysupporting

confidence: 63%

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Intensity Discrimination in the Human Eye

Hecht

Peskin

Patt

1938

Journal of General Physiology

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I Purpose of This ResearchWhen I and [ + AI are two light intensities which can just barely be recognized as different, then the fraction AI/I is considered the measure of intensity discrimination. The value of this fraction and its relation to the intensity f have been the subject of many researches, and these have established that as the intensity Z increases, the fraction A[/I decreases, tending toward a minimum value at the highest intensities. This is true not only for the human eye, but for all other organisms thus far studied, namely, Drosophila, the bee, and Mya (for a summary, see Hecht, 1937 a).Besides the general relation of A[/I to I, the human eye shows an additional phenomenon due to the duality of its retinal structure.There seem to be two relations of A[/I to I, one at the lower intensities representing rod function, and the other at high intensities representing cone function. This rod-cone dichotomy is apparent in nearly all the published measurements from the earliest by Aubert (1865) to the most recent of Steinhardt (1936). In addition, Steinhardt showed that the double function appears only in measurements with central visual fields larger than 2 ° , while the single function appears with fields smaller than 2 ° , and this corresponds to the presence of rods and cones in the larger fields, and to the complete absence of rods in the smaller fields. Moreover, the extent of the low intensity rod section increases with the size of the field because of the increasing number of rods present in comparison with the number of cones.

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Section: Photochemical Theorysupporting

confidence: 81%

Section: O I --Photonssupporting

confidence: 78%

Section: Photochemical Theorysupporting

confidence: 63%

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Intensity Discrimination in the Human Eye

Hecht

Peskin

Patt

1938

Journal of General Physiology

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“…The lines through the data were calculated by using the steady state model that was proposed by Hecht (1935). Although the photochemical hypothesis on which this formula is based has been shown to be an oversimplification, Shlaer (1937) demonstrated that it provides a useful description of the way in which human visual acuity changes with luminance.…”

Section: Resultsmentioning

confidence: 99%

Relationships between luminance and visual acuity in the rhesus monkey

Cavonius¹,

Robbins²

1973

The Journal of Physiology

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SUMMARY1. The ability of rhesus monkeys to detect the gap in Landolt ring testobjects that were presented against background luminances between 5 x 10-5 cd/M2 and 5 x 103 cd/M2 was compared with similar human data.2. At high luminance-levels the acuity of human observers is slightly better than that of rhesus, but rhesus have better acuity at scotopic luminance-levels. Both species have distinct photopic and scotopic acuity functions that cross at 6 x 103 cd/M2.3. The threshold for light detection is estimated to be the same for both species when specified in quanta incident on the retina.4. It is concluded that the receptor and neural mechanisms that mediate visual-acuity function similarly in rhesus and man, and that the differences in acuity that were measured in the two species may be attributed to optical rather than to physiological factors.

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“…If we make the critical frequency f proportional to the concentration x of photoproducts at the steady state, then equation (3) becomes the flicker equation (1) for the cones, provided m = n = 2,.as shown by the data of intensity discrimination (Hecht, 1935). Similarly, when m = 2 and u = 1, equation (3) becomes the same as (2) used for describing the rod data.…”

Section: Theorymentioning

confidence: 99%

Intermittent Stimulation by Light

Hecht

Shlaer

1936

Journal of General Physiology

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200

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Expected ResultsOur previous studies of the relation between light intensity and critical fusion frequency (Hecht and Verrijp, 1933 b) have shown that the differences which the measurements exhibit when they are made in different retinal locations are an expression of the duplex structure of the retina (Schultze, 1866;Parinaud, 1885;yon Kries, 1929). With a centrally located 2 ° field the data are continuous over the whole intensity scale, and may be described by a simple sigmoid curve, whereas with a peripherally located 2 ° field the data divide sharply into a low intensity section and a high intensity section each of which may be described by a single curve. Since the central, 2 ° field falls within the rod-free area of the retina, the continuous nature of the data indicates that they are a function of the cones alone. The double nature of the peripheral measurements very likely represents rod function for the low intensity section and cone function for the high intensity section. This is borne out by the increasing separation of the two sections as measurements are made farther and farther from the center: the cone section shifts to higher intensities and the rod section to lower intensities, as would be expected from the increasing ratio of rods to cones in these regions.In order to confirm the identification of the two sections with rod * A preliminary report of these measurements was made to the Optical Society

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A Theory of Visual Intensity Discrimination

Cited by 86 publications

References 18 publications

Intensity Discrimination in the Human Eye

Intensity Discrimination in the Human Eye

Relationships between luminance and visual acuity in the rhesus monkey

Intermittent Stimulation by Light

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