1,720,972 research outputs found
Spatial image processing for the enhancement and restoration of film, photography and print
No full textDevelopments in the recovery of colour in fine art prints using spatial image processing
No full textPrintmakers have at their disposal a wide range of colour printing processes. The majority of artists will utilise high quality materials with the expectation that the best materials and pigments will ensure image permanence. However, as many artists have experienced, this is not always the case. Inks, papers and materials can deteriorate over time. For artists and conservators who need to restore colour or tone to a print could benefit from the assistance of spatial colour enhancement tools. This paper studies two collections from the same edition of fine art prints that were made in 1991. The first edition has been kept in an archive and not exposed to light. The second edition has been framed and exposed to light for about 18 years. Previous experiments using colour enhancement methods [9,10] have involved a series of photographs that had been taken under poor or extreme lighting conditions, fine art works, scanned works. There are a range of colour enhancement methods: Retinex, RSR, ACE, Histogram Equalisation, Auto Levels, which are described in this paper. In this paper we will concentrate on the ACE algorithm and use a range of parameters to process the printed images and describe these results
User preferences in color enhancement unsupervised methods for printing
No full textIn order to obtain a good quality image in preparation for inkjet printing, the process of adjusting images can be a time consuming and a costly procedure. In this paper, we consider the use of an unsupervised colour enhancement method as part of the automatic pre-processors for printing. Other unsupervised colour enhancement methods are utilised and compared: Retinex, RSR, ACE, Histogram Equalisation, Auto Levels. Test images are subjected to all of the enhancement methods, which are then printed. Users are asked compare each of the sampled images. In all cases, the results are dependent on the image. Thus, we have selected a range of test images: photographs of scenes, reproduction of prints, paintings and drawings. Some of the tested methods are parameter dependent. We do not intend to consider fine tuning for each of the techniques, rather to consider an average parameter set for each one and then test if this approach can aid the decision process of fine tuning. Three user groups are employed: the general user, commercial photographer expert and fine artist. Groups are asked to make a blind evaluation of a range of images (the original and the colour enhanced by the different methods); these are randomly placed. All images are printed on the same printer using the same settings. Users are asked to identify their preferred print in relation to lightness, tonal range, colour range, quality of detail and overall subjective preference
The art and science of colour: Bridging the gap between art and perception
No full textThe paper expounds the concept of bridging of the gap between art and science by considering the relation between colour perception and how computational procedures, which mimic our visual system, have been developed to advance digital imaging techniques in science, photography and art.
How to describe and measure colour is a problematic activity, for colour scientists, designers and artists alike. Furthermore, there is a difference between how the radiometry of colour is measured and how the appearance of colour is perceived. For contemporary colour science, there is a requirement to accurately measure and specify a colour. However when looking at art, at photographs and at real life situations, attempts to define what we ‘see’ are more complex. Pixels with identical radiances, can appear as radically different colours.1
Although separated by over 100 years, parallels can be drawn between the experiments undertaken by Johann Wolfgang von Goethe in the 18th century, and Edwin Land’s research in the 1950s on colour perception that developed into his theory on Retinex (1964). They can be regarded as examples that bridge the gap between biology, physics and art. Through their very different experiments, Goethe and Land attempted to gain a deeper understanding about the relationship between physical and perceptual colour, and how the brain elaborates the physical signal in order to enhance the extraction of visual information – what appears in our brain and what lies in front of us.2 (Tallis, 2008).
Goethe’s interest in human perception as presented in his Farbenlehre (1808)3 attempted to record his many observations on colour phenomena. One of his experiments, using a prism, investigated how fringes of colours appeared and changed according to different black and white patterns; the position of the edges revealed not just spectral colours but also their complementary effect.
Edwin Land is better known for his invention of the instant Polaroid film and camera. Moreover, he was interested in the human visual system, how colour is perceived in relation to its context and through his experiments developed the Retinex theory of colour vision (1964). Land and McCann’s Retinex4 starting with analogue electronics and quickly expanding to digital imagery, used a new approach based on computational algorithms that has made it possible and practical to manipulate images based on spatial methods. These algorithms are currently used for image enhancement, to obtain brighter and more colourful photographic images, but can be also be used to emulate and investigate how colour stimuli appears to our visual system.5, 3
Measuring Colour Constancy and Colour Appearance: an Experiment
No full textColour sensation does not depend strictly on the light signal conveying colour information, but also depends on the arrangement of the visual array of all signals coming from the scene. Colour constancy is one aspect that contributes to the Human Vision System (HVS) in the formation of colour appearance. In the digital-imaging field the concept of colour constancy is often related with a process of trying to identify the object’s reflectance from the light that comes from it. That light is the product of reflectance and illumination. One could separate the reflectance component from the illuminant component, by discounting the illuminant [1]. Although this is claimed to be a useful operation for several applications in computer vision, it is not an accurate description of our human colour appearance mechanism.
Human vision, in fact, does not separate the two components and does not completely eliminate either of the two. HVS developed the ability of normalizing scene appearance across the variation of illuminant and spatial object configuration. In doing this, it is affected not only by the reflectance of the object in the scene and by the spectral content of the illuminants, but also by the spatial array of reflectances and by the spatial non-uniformity of illumination
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