Relative Spectral Sensitivity Research Articles

Divergent photic thresholds in the non-image-forming visual system: entrainment, masking and pupillary light reflex

Light is the principal cue that entrains the circadian timing system, but the threshold of entrainment and the relative contributions of the retinal photoreceptors-rods, cones and intrinsically photosensitive retinal ganglion cells-are not known. We measured thresholds of entrainment of wheel-running rhythms at three wavelengths, and compared these to thresholds of two other non-image-forming visual system functions: masking and the pupillary light reflex (PLR). At the entrainment threshold, the relative spectral sensitivity and absolute photon flux suggest that this threshold is determined by rods. Dim light that entrained mice failed to elicit either masking or PLR; in general, circadian entrainment is more sensitive by 1-2 log units than other measures of the non-image-forming visual system. Importantly, the results indicate that dim light can entrain circadian rhythms even when it fails to produce more easily measurable acute responses to light such as phase shifting and melatonin suppression. Photosensitivity to one response, therefore, cannot be generalized to other non-image-forming functions. These results also impact practical problems in selecting appropriate lighting in laboratory animal husbandry.

Quantitative spectroscopy of the aurora. VI. The auroral spectrum from 275 to 815 nm observed by the OSIRIS spectrograph on board the Odin spacecraft

Terrestrial auroral spectra over the 275 to 815 nm wavelength range have been recorded by the OSIRIS imaging spectrograph on board the Odin spacecraft. The spectra are from the dark polar region and are averaged over limb tangent altitudes from 100 to 105 km. All wavelengths are exposed simultaneously, thus avoiding the effect of temporal intensity variations inherently present in spectrally scanning systems. Particular care has been taken to quantify the relative spectral sensitivity over the entire wavelength range, and there is an estimated 5% precision in the measurements. To maintain accurate on-orbit spectral calibrations, an atmospheric radiation model with multiple Rayleigh scatter is employed to regularly update the OSIRIS spectral response throughout the mission. A calibrated auroral spectrum is presented, together with matching synthetic spectra for many of the observed features, for potential use as a reference spectrum in general atmospheric research. The relative intensities of the brighter auroral band systems and atomic lines are reviewed. Finally, the observed spectrum is made freely available in digital format in long term archives.

Quantitative Algorithm for Melatonin Suppression by Light at Night*

As an important hormone, melatonin has a wide range of functions in human body. Inappropriate light at night (LAN) will cause abnormal human circadian rhythm and then lead to melatonin secretion suppression. Melatonin suppression depends on correlated color temperature (CCT) and wavelengths of LAN. So far there was no quantitative algorithm for melatonin suppression by LAN. A relative spectral sensitivity curve of human plasma melatonin suppression was fitted and an algorithm was presented for predicting melatonin suppression by LAN. Theoretical basis and a method were provided for instructing safety strategy of architectural light at night. Also, the results could be applied in controlling light pollution, formulating the standard of safety nocturnal environment illumination and some other fields.

Toward 1% Photometry: End‐to‐End Calibration of Astronomical Telescopes and Detectors

We review the systematic uncertainties that have plagued attempts to obtain high precision and high accuracy from ground-based photometric measurements using CCDs. We identify two main challenges in breaking through the 1% precision barrier: 1) fully characterizing atmospheric transmission, along the instrument's line of sight, and 2) properly identifying, measuring and removing instrumental artifacts. We discuss approximations and limitations inherent in the present methodology, and we estimate their contributions to systematic photometric uncertainties. We propose an alternative conceptual scheme for the relative calibration of astronomical apparatus: the availability of calibrated detectors whose relative spectral sensitivity is known to better than one part in $10^3$ opens up the possibility of in situ relative throughput measurements, normalized to a precision calibrated detector, using a stable but uncalibrated narrowband light source. An implementation scheme is outlined, which exploits the availability of tunable lasers to map out the relative wavelength response of an imaging system, using a flatfield screen and a calibrated reference photodiode. The merits and limitations of this scheme are discussed. In tandem with careful measurements of atmospheric transmission, this approach could potentially lead to reliable ground-based photometry with fractional uncertainties below the percent level.

An optoelectronic instrument for the determination of sulphite in beverages

The paper describes an optoelectronic device that has been designed and developed to measure the sulphite concentration in beverages for quality evaluation. A selective and sensitive method for determination of sulphite is based on the reaction with pararosaniline acid bleached dye and formaldehyde solution, which gives violet colored complex having absorption maxima at 560 nm. Lambert–Beer’s law is obeyed in the concentration range up to 25 μg/ml (25 ppm) of test solution within an accuracy of ±0.05μg/ml (0.05 ppm). The instrument involves the use of high intensity green light emitting diode (LED) of wavelength 565 nm as light source. BPW21 photodiode having the relative spectral sensitivity above 90% in the range of 500–600 nm has been used as a detector, for the determination of sulphite concentration.

Diagnosing protan heterozygosity using the Medmont C‐100 colour vision test

Background: A surprisingly high 15 per cent of women in Caucasian societies are carriers of the genes for abnormal colour vision but there is no clinical method to identify them. It has long been known that heterozygotes for the protan colour vision deficiencies can demonstrate a reduced luminous sensitivity to red light. This is known as Schmidt's sign, which is thought to arise from mosaicism (Lyonisation). The Medmont C‐100 colour vision test measures relative spectral sensitivity using flicker photometry to differentiate protans and deutans. It should be able to diagnose Schmidt's sign.Method: We tested six known protan heterozygotes (four whose sons have a protan colour vision deficiency and two whose fathers are protan) with the Medmont C‐100 test.Results: All six heterozygotes made average settings of ‐1.75 or more negative at the Medmont C‐100 test, settings which are at or beyond the boundary of the distribution of settings made by observers with normal colour vision. There have been two previous cases reported in the literature of protan heterozygotes, who made protan settings on the Medmont C‐100 or its predecessor test, the OSCAR. We also tested six daughters of the known heterozygotes, 50 per cent of whom are likely to be heterozygotes. Four of the six (66 per cent) made protan settings on the Medmont C‐100. The other two made normal 0.0 settings.Conclusion: We conclude that the Medmont C‐100 can be used clinically to diagnose carriers of protan colour vision deficiency.

Measurement of the Relative Spectral Sensitivity of Photoelectronic Channels of Integral-Type Colorimeters

A method of measuring the relative spectral sensitivity of measurement channels X, Y, and Z of an integral colorimeter is considered. A method of establishing the error of an integral colorimeter over the entire color field of a color chart is proposed on the basis of the optimal integral characteristics of hypothetical light filters and the results of measurements of the relative spectral sensitivity.

Adaptive plasticity during the development of colour vision

Colour vision greatly enhances the discriminatory and cognitive capabilities of visual systems and is found in a great majority of vertebrates and many invertebrates. However, colour coding visual systems are confronted with the fact that the external stimuli are ambiguous because they are subject to constant variations of luminance and spectral composition. Furthermore, the transmittance of the ocular media, the spectral sensitivity of visual pigments and the ratio of spectral cone types are also variable. This results in a situation where there is no fixed relationship between a stimulus and a colour percept. Colour constancy has been identified as a powerful mechanism to deal with this set of problems; however, it is active only in a short-term time range. Changes covering longer periods of time require additional tuning mechanisms at the photoreceptor level or at postreceptoral stages of chromatic processing. We have used the trichromatic blue acara (Aequidens pulcher, Cichlidae) as a model system and studied retinal morphology and physiology, and visually evoked behaviour after rearing fish for 1-2 years under various conditions including near monochromatic lights (spectral deprivation) and two intensities of white light (controls). In general, long-term exposure to long wavelengths light had lesser effects than light of middle and short wavelengths. Within the cone photoreceptors, spectral deprivation did not change the absorption characteristics of the visual pigments. By contrast, the outer segment length of middle and long-wave-sensitive cones was markedly increased in the blue rearing group. Furthermore, in the same group, we observed a loss of 65% short-wave-sensitive cones after 2 years. These changes may be interpreted as manifestations of compensatory mechanisms aimed at restoring the balance between the chromatic channels. At the horizontal cell level, the connectivity between short-wave-sensitive cones and the H2 cone horizontal cells, and the spinule dynamics were both affected in the blue light group. This observation rules out the role of spinules as sites of chromatic feedback synapses. The light-evoked responses of H2 horizontal cells were also sensitive to spectral deprivation showing a shift of the neutral point towards short wavelengths in the blue rearing group. Interestingly, we also found an intensity effect because in the group reared in bright white light the neutral point was more towards longer wavelength than in the dim light group. Like the changes in the cones, the reactions of horizontal cells to spectral deprivation in the long wave domain can be characterised as compensatory. We also tested the spectral sensitivity of the various experimental groups of blue acara in visually evoked behaviour using the optomotor response paradigm. In this case, the changes in the relative spectral sensitivity were more complex and could not be explained by a simple extrapolation of the adaptive and compensatory processes in the outer retina. We conclude that the inner retina, and/or the optic tectum are also involved and react to the changes of the spectral environment. In summary, we have shown a considerable developmental plasticity in the colour vision system of the blue acara, where epigenetic adaptive processes at various levels of the visual system respond to the specific spectral composition of the surroundings and provide a powerful mechanism to ensure functional colour vision in different visual environments. We suggest that processes involving an active fine-tuning of the photoreceptors and the postreceptoral processing of chromatic information during ontogenetic development are a general feature of all colour vision systems. Such mechanisms would establish a functional balance between the various chromatic channels. This appears to be an essential condition for the cognitive systems to extract the relevant and stable information from the unstable and changing stimulus situation.

Physiological ecology of seed germination for the columnar cactus Stenocereus queretaroensis

Responses of seed germination to temperature, water potential, time after harvest, and light were investigated for Stenocereus queretaroensis, a columnar cactus native to west central Mexico. Germination was optimal between 20°C and 30°C, and the germination percentage decreased as the water potential was lowered from 0·00 to −1·0 MPa. Maximal germination of 85% occurred for seeds that were 11 – 28 months old. Germination required light but became light saturated at a photosynthetic photon flux over 10 days of only 0·15 μmol m −2 s −1 (equivalent to a fluence of 67 mmol m −2). Germination was apparently phytochrome mediated, as evidenced by its relative spectral sensitivity (greatest at 660 nm). The environmental requirements for breaking seed dormancy for S. queretaroensis are finely tuned to those typical of the rainy season in its native habitat.

Uncertainty of temperature measurement with thermal cameras

All main international metrological organizations are proposing a parameter called uncertainty as a measure of the accuracy of measurements. A mathematical model that enables the calculation of uncertainty of temperature measurement with thermal cameras is presented. The standard uncertainty or the expanded uncertainty of temperature measurement of the tested object can be calculated when the bounds within which the real object effective emissivity er, the real effective background temperature Tba(r), and the real effective atmospheric transmittance Ta(r) are located and can be estimated; and when the intrinsic uncertainty of the thermal camera and the relative spectral sensitivity of the thermal camera are known.

Long-term light history modulates the light response kinetics of luminosity (L)-type horizontal cells in the roach retina

We have examined the effects of prolonged periods of darkness on the responses of luminosity-type horizontal cells (L-HCs) in the freshwater cyprinid, Rutilus rutilus. Two groups of retinae were compared, those recorded after 10 min dark adaptation (SA) and those recorded after 3 h dark adaptation (LA). The results suggest that long-term light history does not modify the general responsiveness of the L-HCs in this species. However, there are apparent changes in the receptive field of the cells and modifications to the kinetics of the light-evoked response. The kinetics changes involve both a delay in the onset of light response and a selective effect on the hyperpolarizing light-ON response. Thus the mean time constant ( τ) for the SA cells was 32.4±2.39 ms ( n=62), whilst that for the LA cells was 53.4±3.03 ms ( n=61). These effects occur in the absence of changes in the relative spectral sensitivity or threshold sensitivity of the HCs. The results suggest that in some vertebrate retinae, prolonged darkness (light-history) may regulate long-term plasticity in the kinetics of the cone–HC pathway.

S-cone ERGs elicited by a simple technique in normals and in tritanopes

Purpose: to measure changes in the relative spectral sensitivities of the dark adapted and light adapted ERG and thus to establish the possible contribution of rods to the ‘blue cone’ ERG elicited by flashes of blue light. Background: short wavelength stimuli in the light-adapted eye evoke small rounded b-waves which have been considered to be S-cone responses. We have recorded such responses from tritanopes, which called the assumptions into question. Methods: small ERGs were recorded to blue and green flashes. The stimulus was a Ganzfeld which employed light emitting diodes. ERGs were obtained in both the dark-adapted eye and after light adaptation to intense orange light (peak wavelength 610 nm). The change in sensitivity with light adaptation and the relative spectral sensitivity was determined from the voltage/log light intensity functions, using a 10 μV criterion. Results: (1) peak times and changes in sensitivity did not help distinguish light-adapted rod from possible S-cone responses; (2) analysis of the change in the ratio of blue:green sensitivity from darkness to 4.4 log Td. 610 nm background suggests that in seven normal subjects, 90% or more of the ERG evoked by 440 nm flashes is generated by S-cones; (3) three tritanopes have insignificantly reduced S-cone responses. Conclusions: (1) clinical techniques used to isolate S-cone ERGs are appropriate; (2) there are at least two types of tritanope and in those we investigated, functional S-cones are probably displaced into the retinal periphery.

The Wet Collodion Process—A Scientific Approach

The wet collodion process was the first successful photographic negative process. The tone and detail reproduction of both negatives and prints are remarkably good. There are a lot of collodion plates still in existence, but detailed knowledge of how the excellent image quality was achieved has been lost. The Institute of Applied Photophysics in Dresden, Germany, harbors the photographic work of the German pioneer Hermann Krone (1827–1916). He became prominent after using the wet collodion method for landscape photography in 1853. It is extremely difficult to make satisfactory reproductions from those historic negatives on contemporary photographic materials or to digitize the old pictures. The aim of the present work is to gain knowledge of how to reproduce satisfactorily the tone and detail of wet collodion negatives and prints on modern materials. To gain more knowledge of the process, wet collodion layers were poured and then investigated using tools of modern imaging science. Sensitometric curves and relative spectral sensitivities were investigated for a range of emulsions with varying iodide–bromide ratios. Granularity noise and resolution were measured by means of a high-resolution CCD microdensitometer.

Influence of picrotoxin and strychnine on the spectral sensitivity of the turtle ERG b- and d-wave: I. Dark adaptation.

The ERG ON- (b-wave) and OFF-response (d-wave) to differently coloured stimuli was studied using a wide range of stimulus intensities in dark adapted turtle retina. The intensity-response curve of the b-wave showed saturation but that of the d-wave, decline in the high-intensity stimulus range. The curves of the relative spectral sensitivity of the ERG ON- and OFF-response were similar and showed a maximum in the longwave part of the spectrum. GABAergic blockade by 50 mumol L-1 picrotoxin caused an increase of the sensitivity, contrast sensitivity and the amplitude range of both ON- and OFF-responses without narrowing of the response dynamic range. In the range of lower stimulus intensities the ON-responses to blue stimuli and the OFF-responses to red stimuli were affected to a greater extent. An increased ERG b- and d-wave sensitivity was also observed during glycinergic blockade by 50 mumol L-1 strychnine. In the low intensity stimulus range the effect was maximal on the ON-response to blue stimuli and on the OFF-responses to 570 nm stimuli. It was concluded that the GABA- and glycinergic systems in the retina equalize rather than make different the relative spectral sensitivities of the ON- and OFF-responses.

Colour contrast thresholds in congenital colour defectives

The influence of congenital colour defects on a clinical computer test for equiluminous colour discrimination is studied. Differences in relative spectral sensitivity and changes in colour contrast discrimination are two distinct manifestations of the abnormal genes responsible for congenital red-green defects. The very simple and rapid method of the heterochromatic flicker brightness test acts like an anomaloscope and can be used to distinguish protan and deuteran defectives. The depth of the congenital colour defect can be quantified by the colour contrast threshold measured in equiluminous conditions along a single red-green axis identical for all types of red-green colour defectives. Colour contrast thresholds in tritan colour axes are not influenced by congenital red-green defects and therefore they are of extreme clinical interest to detect and quantify acquired colour defects, even in the presence of a previously unknown congenital red-green defect.

Variation in color matching and discrimination among deuteranomalous trichromats: Theoretical implications of small differences in photopigments

Individual differences in abnormal color vision are well known. A fundamental unresolved problem is the great variation in color vision even among those classified as having the same color-vision defect. Several physiological hypotheses have been proposed to account for this variation but little consideration has been given to how (and how much) color matching and discrimination are affected by the posited physiological mechanisms. Advances in molecular genetics have renewed interest in this problem, which is at the foundation of the relation between genotype and phenotype. We report here theoretical Rayleigh ranges (chromatic discrimination) and quantal matches for deuteranomalous trichromats with photopigments in the red/green range that vary in their separation and optical density. The results show there is relatively little loss of discrimination with pigments of normal optical density separated by as little as 2–3 nm. With pigments separated by 4 nm or less, however, optical density can strongly influence discrimination when varied independently in the two types of cone. Moderately lower (or higher) optical density in only one cone-type affects discrimination by altering the shape of the cone's relative spectral sensitivity function. The lack of correlation between Rayleigh-match midpoint and range, which is reported in the literature, may be accounted for by independent variation in pigment separation and optical density.

On a Parallel Structure of the Achromatic Channel in the Human Visual System

The human visual system is a sensory organ having a very high performance. It analyzes various visual information at a very high speed. The key of such performance will be the parallel structure of the visual system. As the fundamental process of the human visual system, the authors pay attention to the achromatic information processing system. In order to elucidate mechanism of the achromatic channel, in the present paper, the achromatic perception has been measured by three psychological experiments. In the first experiment, the spatial characteristic of the achromatic perception has been measured for six wavelengths of monochromatic light. In the second experiment, the relative spectral sensitivity of the achromatic perception has been measured for two test sizes. In the third experiment, the relative spectral sensitivity of the achromatic perception has been measured for two background levels, i.e., at 55 and 798 Td. It is difficult to explain the experimental results by the conventional achromatic channel model, and the experimental results suggest that the achromatic information is processed by several subsystems in parallel. In order to explain the experimental results, we propose a model of achromatic information processing composed of five stages and three subsystems.

Artificial lighting in poultry houses: Are photometric units appropriate for describing illumination intensities?

Abstract 1. The quality and the quantity of poultry house lighting are important. Many research projects have been centred on temporal aspects of this illumination and on its spectral distribution ('colour') and illumination intensity. For this purpose illumination is measured at floor‐level in photometric units (lux or cd/m2). 2. The relevance of these measurements depends on an equivalence of the domestic fowl and the human photopic spectral sensitivity curves, because the latter (CIE) type of curve is the basis of photometric units. 3. A comparison of the data on domestic fowl spectral sensitivity and the CIE‐data, however, shows a serious discrepancy. For most purposes in poultry research, therefore, the lux‐meter is not an appropriate instrument. 4. A better way of presenting the relative luminance of a lamp for domestic fowl ('galluminance') is by multiplying the spectral power distribution of the lamp (Eλ)—as documented by the manufacturer— by the relative spectral sensitivity distribution of the domestic fowl (Gλ). 5. For this purpose we present the log Gλ data in relative units per 5 nm.

Light-activated heterotrophic growth of the cyanobacterium Synechocystis sp. strain PCC 6803: a blue-light-requiring process

A glucose-tolerant strain of Synechocystis sp. strain 6803 will not grow on glucose under complete darkness unless given a daily pulse of white light, typically 5 min of 40 mumol m-2 s-1 (light-pulsed conditions). The light pulse is insufficient for photoautotrophy, as glucose is required and growth yield is dependent on glucose concentration. Growth rate is independent of fluence, but growth yield is dependent on fluence, saturating at 40 to 75 mumol m-2 s-1. A Synechocystis strain 6803 psbA mutant strain grows under light-pulsed conditions at rates similar to those for the glucose-tolerant strain, indicating that photosystem II is not required for growth. The relative spectral sensitivity of the growth of light-pulsed cultures (growth only in blue light, 400 to 500 nm, maximum at 450 nm) precludes energetic contribution from cyclic electron transport around photosystem I. Pulses of long-wavelength light (i.e., 550 and 650 nm) did not support the growth of Synechocystis strain 6803 and, when supplied before or after a blue-light pulse, did not inhibit blue-light-stimulated growth of Synechocystis strain 6803. We conclude that the required blue-light pulse does not support growth via photosynthetic electron transport but appears instead to function as an environmental signal regulating heterotrophic metabolism, cell division, or other photomorphogenic processes. We have termed the growth of Synechocystis strain 6803 pulsed with light and kept otherwise in complete darkness light-activated heterotrophic growth. This observation of a blue-light requirement for the growth of Synechocystis strain 6803 represents a novel blue light effect on the growth of a cyanobacterium.

Characterization of adaptation in phototropism of Arabidopsis thaliana.

Phototropic curvature has been measured for etiolated Arabidopsis thaliana seedlings with and without a preirradiation. A bilateral preirradiation with 450-nm light at a fluence greater than about 0.1 micromole per square meter causes a rapid desensitization to a subsequent 450-nanometer unilateral irradiation at 0.5 micromole per square meter. Following a refractory period, the capacity to respond phototropically recovers to the predesensitization level, and the response is then enhanced. The length of the refractory period is between 10 and 20 minutes. Both the time needed for recovery and the extent of enhancement increase with increasing fluence of the bilateral preirradiation. Based on the relative spectral sensitivities of desensitization and enhancement, these responses can be separated. Desensitization is induced by blue light but not by red light. Enhancement, however, is induced by both blue and red light. Thus, enhancement can be induced without desensitization but not vice versa. Both desensitization and enhancement affect only the magnitude of the response and do not affect the fluence threshold.