FDM 3D printers allow massive creativity in personal products, but their potential has been limited due to inability to manipulating material properties. Previous work had demonstrated that the desired roughness could be presented simply by controlling the spatial density of tiny pins on a printed surface. This article offers a means of providing the desired softness perception of a printed surface and the desired roughness to expand the haptic dimension over which a user can exert control. Specifically, we control the softness by manipulating the infill structures of a printed surface. However, it is known that a skin contact area affects softness perception. The roughness, which is controlled by pins' density, may also affect the perceived softness of a printed surface. Therefore, we investigate how the internal structures and the density of the pins affect softness perception. Through psychophysical experiments, we derive a computational model that estimates the perceived softness from the density of the pins and the infill density of a printed surface. c 2021 Society for Imaging Science and Technology.
We investigated spatio-chromatic contrast sensitivity in both younger and older color-normal observers. We tested how the adapting light level affected the contrast sensitivity and whether there was a differential age-related change in sensitivity. Contrast sensitivity was measured along three directions in colour space (achromatic, red-green, yellowish-violet), at background luminance levels from 0.02 to 2000 cd/m2, and different stimuli sizes using 4AFC method on a high dynamic range display. 20 observers with a mean age of 33 y. o. a. and 20 older observers with mean age of 65 participated in the study. Within each session, observers were fully adapted to the fixed background luminance. Our main findings are: (1) Contrast sensitivity increases with background luminance up to around 200 cd/m2, then either declines in case of achromatic contrast sensitivity, or remains constant in case of chromatic contrast sensitivity; (2) The sensitivity of the younger age group is higher than that for the older age group by 0.3 log units on average. Only for the achromatic contrast sensitivity, the old age group shows a relatively larger decline in sensitivity for medium to high spatial frequencies at high photopic light levels; (3) Peak frequency, peak sensitivity and cut-off frequency of contrast sensitivity functions show decreasing trends with age and the rate of this decrease is dependent on mean luminance. The data is being modeled to predict contrast sensitivity as a function of age, luminance level, spatial frequency, and stimulus size.
In images, the representation of glossiness, translucency, and roughness of material objects (Shitsukan) is essential for realistic image reproduction. To date, image coding has been developed considering various indices of the quality of the encoded image, for example, the peak signal-to-noise ratio. Consequently, image coding methods that preserve subjective impressions of qualities such as Shitsukan have not been studied. In this study, the authors focus on the property of glossiness and propose a method of glossiness-aware image coding. Their purpose is to develop an encoding algorithm that produces images that can be decoded by standard JPEG decoders, which are commonly used worldwide. The proposed method consists of three procedures: block classification, glossiness enhancement, and non-glossiness information reduction. In block classification, the types of glossiness in a target image are classified using block units. In glossiness enhancement, the glossiness in each type of block is emphasized to reduce the amount of degradation of glossiness during JPEG encoding. The third procedure, non-glossiness information reduction, further compresses the information while maintaining the glossiness by reducing the information in each block that does not represent the glossiness in the image. To test the effectiveness of the proposed method, the authors conducted a subjective evaluation experiment using paired comparison of images coded by the proposed method and JPEG images with the same data size. The glossiness was found to be better preserved in images coded by the proposed method than in the JPEG images.
We evaluate improvements to image utility assessment algorithms with the inclusion of saliency information, as well as the saliency prediction performance of three saliency models based on successful utility estimators. Fourteen saliency models were incorporated into several utility estimation algorithms, resulting in significantly improved performance in some cases, with RMSE reductions of between 3 and 25%. Algorithms designed for utility estimation benefit less from the addition of saliency information than those originally designed for quality estimation, suggesting that estimators designed to measure utility also measure some degree of saliency information, and that saliency is important for utility estimation. To test this hypothesis, three saliency models are created from NICE and MS-DGU utility estimators by convolving logical maps of image contours with a Gaussian function. The performance of these utility-based models reveals that highlyperforming utility estimation algorithms can also predict saliency to an extent, reaching approximately 77% of the prediction performance of state-of-the-art saliency models when evaluated on two common saliency datasets.
High dynamic range (HDR) imaging has become an important topic in both academic and industrial domains. Nevertheless, the concept of dynamic range (DR), which underpins HDR, and the way it is measured are still not clearly understood. The current approach to measure DR results in a poor correlation with perceptual scores (r ≈ 0.6). In this paper, we analyze the limitations of the existing DR measure, and propose several options to predict more accurately subjective DR judgments. Compared to the traditional DR estimates, the proposed measures show significant improvements in Spearman's and Pearson's correlations with subjective data (up to r ≈ 0.9). Despite their straightforward nature, these improvements are particularly evident in specific cases, where the scores obtained by using the classical measure have the highest error compared to the perceptual mean opinion score.
The purpose of artistic practice has frequently been to translate human visual experience into pictures. By viewing these pictures we can retrospectively share something of the world the artist saw, and the way he or she saw it. Over the centuries artists have evolved highly refined methods for depicting what they see, and the works they produce can provoke strong emotional, aesthetic, and perceptual responses. Looking at a painting by Vincent van Gogh of a vase of sunflowers, for example, can be more thrilling and memorable than seeing a real vase of sunflowers, or even a photograph of the same scene. Why do we respond so strongly to artistic depictions of everyday scenes? The hypothesis considered here is that artists do not attempt to faithfully record reality. Rather, they select and manipulate visual information in ways that are tuned to our subjective experience. I will discuss some of the techniques artists have used to achieve this, and consider how they might be relevant to those designing new forms of imaging technologies in order to improve how they represent visual experience.
Recently the movie industry has been advocating the use of frame rates significantly higher than the traditional 24 frames per second. This higher frame rate theoretically improves the quality of motion portrayed in movies, and helps avoid motion blur, judder and other undesirable artifacts. Previously we reported that young adult audiences showed a clear preference for higher frame rates, particularly when contrasting 24 fps with 48 or 60 fps. We found little impact of shutter angle (frame exposure time) on viewers' choices. In the current study we replicated this experiment with an audience composed of imaging professionals who work in the film and display industry who assess image quality as an aspect of their everyday occupation. These viewers were also on average older and thus could be expected to have attachments to the "film look" both through experience and training. We used stereoscopic 3D content, filmed and projected at multiple frame rates (24, 48 and 60 fps), with shutter angles ranging from 90° to 358°, to evaluate viewer preferences. In paired-comparison experiments we assessed preferences along a set of five attributes (realism, motion smoothness, blur/clarity, quality of depth and overall preference). As with the young adults in the earlier study, the expert viewers showed a clear preference for higher frame rates, particularly when contrasting 24 fps with 48 or 60 fps. We found little impact of shutter angle on viewers' choices, with the exception of one clip at 48 fps where there was a preference for larger shutter angle. However, this preference was found for the most dynamic "warrior" clip in the experts but in the slower moving "picnic" clip for the naïve viewers. These data confirm the advantages afforded by high-frame rate capture and presentation in a cinema context in both naïve audiences and experienced film professionals. © 2016 Society for Imaging Science and Technology.