Relative Spectral Sensitivity Research Articles

Objective Method of Measuring the Relative Spectral-Luminosity Curve in Man

Steady-state evoked potentials were recorded from the human scalp and subjected to Fourier analysis during the psychophysical procedure of heterochromatic flicker photometry. The amplitudes of harmonic components whose frequencies fell in the range roughly 45–55 cps showed a clear minimum. This minimum coincided with the point of minimum subjective flicker. This agreement did not generally hold either for harmonic components in the range 13–22 cps nor for the peak-to-peak amplitude of the averaged evoked potential. Relative spectral-sensitivity curves derived both from psychophysical and evoked-potential data agreed within 0.07 log units (18%). The objective method described below is considerably more precise, and is less affected by evoked-potential variability, than previous methods that used evoked-potential amplitude to measure spectral sensitivity. A complete spectral-sensitivity curve can be obtained in two sessions of 212 h each, and the procedure could probably be shortened significantly.

Spectral sensitivities of wolf spider eyes.

ERG's to spectral lights were recorded from all eyes of intact wolf spiders. Secondary eyes have maximum relative sensitivities at 505-510 nm which are unchanged by chromatic adaptations. Principal eyes have ultraviolet sensitivities which are 10 to 100 times greater at 380 nm than at 505 nm. However, two animals' eyes initially had greater blue-green sensitivities, then in 7 to 10 wk dropped 4 to 6 log units in absolute sensitivity in the visible, less in the ultraviolet. Chromatic adaptations of both types of principal eyes hardly changed relative spectral sensitivities. Small decreases in relative sensitivity in the visible with orange adaptations were possibly retinomotor in origin. Second peaks in ERG waveforms were elicited from ultraviolet-adapted principal eyes by wavelengths 400 nm and longer, and from blue-, yellow-, and orange-adapted secondary eyes by wavelengths 580 nm and longer. The second peaks in waveforms were most likely responses of unilluminated eyes to scattered light. It is concluded that both principal and secondary eyes contain cells with a visual pigment absorbing maximally at 505-510 nm. The variable absolute and ultraviolet sensitivities of principal eyes may be due to a second pigment in the same cells or to an ultraviolet-absorbing accessory pigment which excites the 505 nm absorbing visual pigment by radiationless energy transfer.

The Spectral Sensitivity and the Components of the Visual System in the Stemmata of Silkworm Larvae, Bombyx mori L. (Lepidoptera : Bombycidae)

The electroretinograms (ERGs) of the stemmata of silkworm larvae were recorded with the active electrode on the proximally blocked ocellar nerve and the reference electrode in the abdomen. From the responses to various intensities of monochromatic lights of wavelength 340 to 638 mμ, response-log relative intensity curves were obtained. These curves are not parallel among different wavelengths. These curves were used to construct the spectral sensitivity curve by deducing the relative number of quanta required to evoke a constant response. The spectral sensitivity curves showed one peak in the near ultraviolet and another hump or peak in the blue-green or green region of the spectrum. The latter peak was more prominent at lower intensities than at higher ones. Monochromatic light adaptation selectively influenced the relative spectral sensitivity and the form of the ERGs, suggesting that two receptor systems (UV and G) exist in the silkworm stemmata, which differ in spectral sensitivity and which may mediate true color vision. As a clue to find the spectral sensitivities of the individual receptor systems, color specific difference in the latency of the ERGs was utiliized. Two hypothetical spectral sensitivity curves thus obtained considerably overlapped and that of the G-receptor system showed a peak at about 540 mμ. However, no exact position of the maximum sensitivity of the UV-receptor system could be illustrated.

The Sensitivity of Nonlinear Detectors

Starting from the general concept of sensitivity as the quotient of effect by cause, the differential spectral and relative spectral sensitivities of a radiation detector are derived. If the effect is not proportional to the cause, it is shown that a relative spectral sensitivity without restrictions may be defined only by referring to equal effect but not to equal cause. Some consequences of this condition are discussed.

Spectral sensitivity of the white rat by a training method

Albino Norway rats were trained to run repeatedly to a light stimulus in a modified Y-maze for a food reward. The sequence of left and right stimuli, and the reward, were automatically controlled. The stimulus intensity, which was changed automatically according to the rat's success, was recorded, and a frequency-of-seeing graph, derived from it, gave an estimate of threshold. The rats showed prolonged dark adaptation. The relative spectral sensitivity, after 90 min in darkness, showed maximum sensitivity near 500 nm. Light adaptation produced little change in relative sensitivity. There is good agreement with Dodt and Echte's (1961) ERG results.

A thermal component of excitation in the lateral eye of Limulus.

1. The temperature dependence of the relative spectral sensitivity of the excised lateral eye of Limulus was examined using its electrical response to light.2. At wave-lengths longer than 625 mmu lowering the temperature from 27 to 7 degrees C reduced the relative spectral sensitivity, while no effect was measurable at shorter wave-lengths.3. The reduction in relative sensitivity increased linearly with decreasing wave number.4. The observations support the hypothesis that a critical amount of energy (activation energy) must be supplied to the photopigment molecule in order that it excite the photoreceptor. Quanta with energy lower than the activation energy are effective only if the thermal energy of the molecule can supply the deficit.5. The lower limit of the activation energy for the photoreceptor of the lateral eye of Limulus determined from the results of this study is 44 kcal mole(-1).

Cone activity in the light-induced response of the human electro-oculogram.

Spectral sensitivity of the light-induced response of the human electro-oculogram has been measured at three spectral locations (λ max 472, 572 and 618 mμ). It was found that, at 572 and 618 mμ the relative average spectral sensitivity was higher than predicted by the CIE scotopic luminosity curve, but lower than predicted by Walds spectral sensitivity curve of human parafoveal cones. The results indicate cone activity in the light-induced EOG response.

SPECTRAL SENSITIVITY OF SINGLE UNITS IN THE OPTIC TECTUM OF THE GOLDFISH.

Action potentials evoked by a small light in the visual field were recorded from single units in the optic tectum of the goldfish. The relative spectral sensitivity of these responses was measured by determining the threshold energy of the stimulus light at 22 wavelengths from 341 to 779 mµ.After dark adaptation the spectral sensitivity of "on", "off" and "on‐off" units was the same, with a maximum at about 533 mµ and fitted the absorption spectrum of porphyropsin.After light adaptation some "on" and some "off" units had a spectral sensitivity curve which fitted the absorption spectrum of cyanopsin with a maximum at about 620 mµ. Most units had a narrow photopic spectral sensitivity curve: in some units there was a single maximum, usually in the range 605‐651 mµ. but in some "on‐off" units the maximum sensitivities of "on" and of "off" responses were different. There were three classes of these units: R‐G units (sensitivity maxima at 630‐651 mµ and 497‐517 mµ), R‐B units (maxima 605‐651 mµ and 462 ±14 mµ) and Y‐B units (maxima 552‐605 mµ and 462±14 mµ). The neutral point, at which "on" and "off" responses had the same sensitivity, was at 552‐584 mµ in R‐G units, at 517‐552 mµ in R‐B units and at 497‐517 mµ in Y‐B units.The results indicate that the goldfish has a rod pigment with its absorption maximum at about 533 mµ, and that there are at least two cone pigments with absorption maxima at about 467 mµ and 620 mµ. It is suggested that antagonism between two sets of cones, each set containing one of three pigments with absorption maxima at 467, 533 and 620 mµ could account for the observed sensitivity maxima and neutral points of R‐G, R‐B and Y‐B units.

Physical Approximation of Color-Mixture Functions

One of the most important problems in photoelectric colorimetry is the duplication, by physical means, of a given set of color-mixture functions. Several methods are outlined in this paper for the numerical derivation of close approximations to given color-mixture functions using the relative spectral-sensitivity function of a photoelectric receiver and the spectral transmittances of glass filters. The filters are placed either in series or side by side between the source and the receiver. Numerical examples illustrate the methods.

General basis for quantitative Raman analyses

Abstract A general scheme of quantitative Raman analysis has been developed which avoids to a large degree the effects of sample composition and various instrumental factors on the observed scattering coefficients. Measurements are made in solution with a perpendicular Polaroid filter around the sample. The solvent is used as an internal standard. Band intensities are measured above a linear base line to correct for background. The method provides for the effects of partial polarization of the Raman radiation and for changes in the relative spectral sensitivity. Samples which are colored or fluoresce excessively cannot be analyzed by this method.

General basis for quantitative Raman analyses

A general scheme of quantitative Raman analysis has been developed which avoids to a large degree the effects of sample composition and various instrumental factors on the observed scattering coefficients. Measurements are made in solution with a perpendicular Polaroid filter around the sample. The solvent is used as an internal standard. Band intensities are measured above a linear base line to correct for background. The method provides for the effects of partial polarization of the Raman radiation and for changes in the relative spectral sensitivity. Samples which are colored or fluoresce excessively cannot be analyzed by this method.

The colour change of monochromatic light with retinal angle of incidence.

The few previous measurements of the small change of apparent colour of a monochromatic light stimulus when its angle of incidence on the foveal retina is varied (or SC II effect), have been confined to changes of apparent hue. A differential, three-colour mixture method, with alternating instead of juxtaposed presentation of the test and comparison stimuli, has now been applied to determine the complete colour change, hue and saturation. For the main subject, the results show hue shifts of the expected kind and a small but significant supersaturation of the apparent colour of an obliquely, compared with a normally incident stimulus, in the wavelength range 485 to 510 mµ. From earlier qualitative observations, such a supersaturation appears to occur for most subjects. The SC II colour changes are attributable to differences in the directional response of the receptors associated respectively with the three colour systems of the trichromatic scheme. From the relative spectral sensitivities of these systems...

Spectral sensitivity of single neural units in the bullfrog retina.

Nerve impulses from retinal units, presumably ganglion cells, were elicited by calibrated light flashes of various luminances, wavelengths, and durations, delivered to the eye of the intact bullfrog under scotopic and photopic conditions. Although several response measures were utilized, latency to the first impulse was particularly useful. A simple linear function relating reciprocal of latency to log light luminance was associated with the dark-adapted state and more complex latency-luminance functions were associated with the light-adapted state. Spectral sensitivity curves were derived from these latency-luminance functions by determining the relative energy at the various wavelengths required to produce a criterion latency. A wide variety of relative spectral-sensitivity curves were found. The average shift of spectral sensitivity toward the longer wavelengths (Purkinje shift) between scotopic and photopic conditions was in approximate quantitative agreement with a shift from the rhodopsin to the iodopsin absorption spectrum. The Purkinje shift was also seen in the results obtained from some individual neural units. Among the variety of spectral sensitivity curves obtained from the 20 dark-adapted units, a homogeneous group of curves (11 units) was identified which was well fitted by the rhodopsin absorption curve. Of the 16 light-adapted units, one group (7 units) was roughly fitted by the iodopsin curve. Of special interest to color theory are the units not included in the rhodopsin or iodopsin groups. While none of the curves were completely fitted by Granit’s modulators, many of the sensitivity peaks were at wavelengths that correspond to his green and red modulators (frog). Relatively narrow spectral-sensitivity curves with maxima below 450 mμ were obtained from several of the dark-adapted units; these were reliably different from Granit’s blue modulator (frog) and were approximately fitted by Dartnall’s blue-sensitive pigment.

Spectral Sensitivity Determinations by Cutoff Filters

A series of 26 selenium glass filters with cutoffs uniformly paced over the visible spectrum is used as the basic set of filters to determine the relative spectral sensitivity function of a given photoelectric receiver. Certain characteristics of these filters, such as non-uniformity of transmittance across the filter surface and temperature dependence, impair the precision of the transmittance measurements as well as photocell-response measurements. Nevertheless it is possible to derive fairly well-conditioned matrices of difference functions obtained from the basic set of cutoff filters, which will allow a satisfactory determination of a spectral sensitivity function. Experimental as well as numerical implications are discussed in detail on the basis of a practical example.

Die Spektralsensitivität von Insekten-Komplexaugen im Ultraviolett bis 290 mμ

Behaviour experiments have shown that insects react to ultraviolet light. Almost no data are available within this spectral range, however, on the sensitivity of their light sense organs. In this investigation the relative spectral sensitivity (1/Q) of the compound eye of the fly, Calliphora erythrocephala, and various areas of the compound eye of the cockroach, Periplaneta americana, was measured including the ultraviolet range down to 290 mμ. Equal amplitudes of the electroretinogram indicated equal efficiencies of the stimuli. The sensitivity curve in both species shows, besides the known maximum in the blue green, a second maximum in the ultraviolet. This second maximum was found between 341-369 mμ depending on the species and the particular area of the eye. At still shorter wave lengths sensitivity decreases. In the fly eye and the upper part of the cockroach eye the sensitivity maximum in the ultraviolet is higher than in the bluegreen, whereas in the ventral part of the cockroch eye it is lower. Monochromatic light adaptation selectively influences the relative sensitivity of the upper part of the cockroach eye. The sensitivity curves are discussed with regard to visual pigments and types of receptors. Fluorescence of the eye media is considered to have only negligible if any influence on the high sensitivity for ultraviolet light.

Electroretinographic measurement of spectral sensitivities of the albino eye in direct and diascleral light

The relative spectral sensitivity of the dark adapted rabbit eye was measured by means of the electroretinogram. As already reported this is modified in albino rabbits by the reflection of blood behind the visual cells.

Spectral sensitivity and the threshold of gecko eyes; electroretinographical studies on Hemidactylus turcicus & Tarentola mauritanica

Retinal activity in two species of nocturnal gecko, Tarentola mauritanica and Hemidactylus turcicus, was studied by means of electroretinography. The electroretinogram of T. mauritanica resembled that of the frog in having a positive off-effect especially when light-adapted. In H. turcicus the electroretinogram for single stimuli resembled that of the rabbit, showing a strong secondary rise after the b-wave and no off-effect even in the light-adapted state. Responses to a fixed slow rate of flicker were seperate at low intensities, but became fused if high intensity stimuli were used. This phenomenon has already been observed in human rod monochromats. The relative spectral sensitivity of the b-wave was measured in both species for wavelengths between 341 and 673 mμ (pupil dilated, large retinal area stimulated). During dark adaptation the maximum sensitivity was at about 530 mμ; this corresponds roughly with the observations of other workers using different methods. The shapes of the sensitivity curves of both species are, however, unusually broad, much more so than the absorption spectrum of any photopigment so far extracted. This, together with a fall in sensitivity to the short wavelengths as a result of light adaptation in H. turcicus suggests that more than one photopigment is present. Both species have a high dark-adapted sensitivity: In both T. mauritanica and H. turcicus the dark-adapted threshold compared to that of the cat measured under comparable conditions was about ten (0.3 to 1.7 log units) times lower.

Measurement of Relative Spectral Sensitivity of Photographic Materials

Measurement of Relative Spectral Sensitivity of Photographic Materials

Changes induced in spectral sensitivity and form of retinal action potential of the cockroach eye by selective adaptation

The relative spectral sensitivity and the shape of the slow monophasic action potential of the compound eye of the cockroach, Periplaneta americana L., were investigated using monochromatic light for stimulation and adaptation. It was demonstrated that different areas of this eye differ in function. Ventral parts show a one-peak spectral sensitivity curve (maximum at about 507 mμ) which is unaltered by the state of adaptation. Spectral sensitivity of areas at the upper edge of the eye shows the same maximum as a result of dark adaptation, but the sensitivity curve rises towards violet wavelengths. Adaptation with monochromatic light changes the relative spectral sensitivity considerably. Colour specific differences in the shape of the action potential are seen in the latter areas only. The results indicate that two receptor systems exist in the cockroach eye, which differ in spectral sensitivity and which may mediate true colour vision, at least in the blue-green and violet range of the spectrum. The meaning of the different time course of potentials following stimulation with different colours is discussed.

Photoptic dominator and color components in the human electroretinogram

The relative spectral sensitivity of the photopic component of the human electroretinogram was measured for wave lengths between 404 and 672 mμ in a state of moderate light adaptation. Light stimuli at a constant frequency of 32 per second were used to avoid scotopic contamination.