Search results for "luminance"
showing 10 items of 76 documents
On saturation and related parameters following Guth's ATD colour-vision model
2001
In this work, we have examined the influence of different parameters both on perceived saturation and saturation discrimination with unrelated colours, on the basis of S. L. Guth's CA90 colour-vision model and its subsequent modifications. Our analysis of perceived saturation covered (1) spectral saturation functions at constant luminance, (2) saturation functions in constant colorimetric purity loci, (3) saturation vs. colorimetric purity functions, (4) saturation vs. luminance functions in the 1–1000 td range, and, finally, (5) the equal saturation loci in the xy color diagram. Regarding saturation discrimination, we focused on (1) saturation thresholds from white and from the locus, (2) …
The effect of predator appetite, prey warning coloration and luminance on predator foraging decisions
2010
AbstractAposematic prey advertise their defence to visually hunting predators using conspicuous warning colouration. Established theory predicts that aposematic signals should evolve towards increased conspicuousness and similarity to enhance predator education. Contrary to theoretical expectations, there is often considerable within- and between-species variation in aposematic signals of animals sharing the same ecological niche, phylogeny and predators. This may be explained by varying responses of predators that weaken the selection pressure for a consistent signal. By presenting painted mealworm larvae as prey to great tits as predators we tested if different aposematic colour patterns …
Sizing analysis of interior lighting using tubular daylighting devices
2017
Abstract Daylight access and indoor thermal comfort are key issues for high design level of sustainable buildings. In fact, daylight provides energy savings and visual comfort condition that can foster higher productivity and performance. This paper proposes a case study of sizing of daylight devices for zenith light. It enables the decision-making process of the designer to reach high levels of daylight factor. The proposed method is shown with an example of application. For the case study, a room in south of Italy, 24 different solar tunnels configurations and 12 cases with different number of skylights have been evaluated.
Questionnaires and simulations to assess daylighting in Italian university classrooms for IEQ and energy issues
2021
Abstract Results from the DAYKE-Italy project are presented. An investigation on daylighting in eight classrooms in five Italian universities was carried out through a combined approach: an ad-hoc survey administered to students to investigate how they perceive daylight in classroom, and numerical simulations (DIVA + ALFA) to calculate a set of objective metrics (daylight, circadian, and energy-related). A sample of 542 questionnaires was collected through two sessions and the subjective judgments were correlated to objective metrics. Results from descriptive and statistical analyses showed: (i) the correlation was significant for all daylight metrics: among them, average daylight factor an…
Perceptually Optimized Image Rendering
2017
We develop a framework for rendering photographic images by directly optimizing their perceptual similarity to the original visual scene. Specifically, over the set of all images that can be rendered on a given display, we minimize the normalized Laplacian pyramid distance (NLPD), a measure of perceptual dissimilarity that is derived from a simple model of the early stages of the human visual system. When rendering images acquired with a higher dynamic range than that of the display, we find that the optimization boosts the contrast of low-contrast features without introducing significant artifacts, yielding results of comparable visual quality to current state-of-the-art methods, but witho…
High-speed motion estimation of fertilizer granules with Gabor filters
2008
In the context of fertilizer supply reduction, the understanding of the whole centrifugal spreading process became essential. Since few years we focused our research on the determination by image processing of the ejection conditions of flight of the granules, that is the trajectories and ejection angles, used as input data for ballistic flight to predict the fertilizer repartition on the ground. Due to relative high speed of the fertilizer granules (around 40 m.s -1 ), the previous parameters were evaluated using a specific high speed imaging system and image processing based on motion estimation method using Markov Random Fields method (MRFs). Even if the results were good (90% of correct…
A Multi-Scale Colour and Keypoint Density-Based Approach for Visual Saliency Detection
2020
In the first seconds of observation of an image, several visual attention processes are involved in the identification of the visual targets that pop-out from the scene to our eyes. Saliency is the quality that makes certain regions of an image stand out from the visual field and grab our attention. Saliency detection models, inspired by visual cortex mechanisms, employ both colour and luminance features. Furthermore, both locations of pixels and presence of objects influence the Visual Attention processes. In this paper, we propose a new saliency method based on the combination of the distribution of interest points in the image with multiscale analysis, a centre bias module and a machine …
Determining the efficiency of optical sources using a smartphone's ambient light sensor
2017
This work reports the use of a smartphone’s ambient light sensor as a valuable tool to study and characterize the efficiency of an optical source. Here, we have measured both luminous efficacy and efficiency of several optical sources (incandescent bulb and halogen lamp) as a function of the electric power consumed and the distance to the optical detector. The illuminance of LEDs as a function of the distance to the optical detector is characterized for different wavelength emissions. Analysis of the results confirms an inverse-square law of the illuminance with the detector–source distance and shows good agreement with values obtained by classical experiments. This experience will trigger …
Space syntax analysis applied to urban street lighting: Relations between spatial properties and lighting levels
2019
According to the international technical standards, higher lighting levels (luminance and illuminance levels) are expected in trafficked and central roads (where restrictive minimum lighting requirements are necessary) and lower lighting levels are expected in peripheral and less trafficked roads. Starting from this assumption, in this paper, the authors analyse the correlations between spatial properties (expressed by spatial indicators, for example, the integration index and the choice index) and lighting levels (expressed by lighting parameters, for example luminance and illuminance) upon roads of an urban context. The analysis has been applied to the case study of the medium sized town …
Analysis of the human a-wave ERG component
2006
The a-wave is one of the main issues of research in the field of ocular electrophysiology, since it is strictly connected with early photoreceptoral activities. The present study proposes mathematical methods that analyse this component in human subjects, and supports experimental evidence relating to possible correlations among the responses of photoreceptoral units under a light stimulus. The investigation is organized in two parts: the first part concerns the onset and the initial slope, up to the first minimum (about 10-15 ms), the second part deals with the main portion of the wave, up to about 30 ms. In both cases, the a-waves, recorded at various levels of luminance, have been fitted…