Highlights on works in Color Imaging Conference 2019 – by PhD students from GDR APPAMAT

03 novembre 2019 par GDR APPAMAT
The GDR APPAMAT offered a grant to PhD students to attend Color Imaging Conference in Paris, 23-25 october 2019. Aiman Raza, Dorian Saint-Pierre and Maëlle Vilbert accepted to highlight one of the works which caught their attention during the conference.

Evaluation and modificiation of von kries chromatic adaptation transform.

Shining Ma et al.

 The Von Kries chromatic adaptation used in CAT02 has been a subject of constant tests and modifications but not many had similarly significant application for warmer SPDs (CCT~<3000K, Illuminant A or monochromatic yellow-orange SPDs). This study proposed an optimized chromatic transform with a scaling factor to modulate the s-cones chromatic adaptation as per the test source CCT. With this methodology we can take into account the unequal distribution between the short wavelength cones and the medium-large cones in warmer CCTs. The resulting adjusted chromatic transform was tested on an exhaustive number of light sources-background chromaticity pairs and shows a significant reduction in DeltaE2000 between the observed color and the predicted color of the reference sample. The study also highlights the importance of a larger field of view to reduce intra observer and inter observer variability, which further reduces error. All in all, a very promising article with a thorough literature review that can also be used by beginners to understand in details all the different modifications through time on the chromatic adaptation transforms.

Highlighted by Aiman Raza


Printing with Light: Daylight-fluorescent Inks for Large-gamutMulti-color Printing

Peter Morovic et al.

Printing with specialty inks such as fluorescent ones often comes with the cost of developing a specific workflow that goes beyond the constraints of normal printing solutions. In this paper, Peter and Jan Morovic from the HP Labs investigate the possibility to use daylight-fluorescent inks added to a classical set of primaries, in order to extend the existing color gamut available in conventional printers. They used the Halftone Area Neugebauer Separation (HANS) pipeline to tackle the obstacle of having to make precise inks combinations before printing. This issue was met in previous studies. This way they were able to access any ink coverage using both reflective and fluorescent properties.

They built several subsets of color, one of them being a CMRYK, where the chosen fluorescent ink corresponding to “R” is the Rhodamine B, a pure pink photoluminescent ink.  This combination of inks resulted in a 64% expansion of the original CMYK gamut! To validate this experimentally, a specific spectral model had to be designed and trained to handle measurements done by a conventional spectrophotometer. In the future, any additional data can and will be used to further this model, putting aside the need to measure the fluorescence with a specific device.

 This study lays a solid basis to later apprehend a printing process where fluorescent could be considered as usual process colors resulting in bigger printing gamuts and more vivid image than ones printed with classic solid colors.

Highlighted by Dorian Saint-Pierre


Color Vision Differences Following Retinal Detachment and Subsequent Cataract Surgery

Susan Farnand et al.

Quantification of colour vision changes due to eye surgery from the internal point of view of a colour scientist: this is an approach I would not have expected while attending CIC 27. According to her own experience, Susan Farnand from Munsell Color Science Laboratory, Rochester Institute of Technology, rigorously described the close follow-up of her 2017 retinal detachment treatment and her subsequent cataract surgery. She quantified color perception changes every ten days during the operation recoveries, using standard Color Matching procedures (DeltaE00 between her two eyes), D&H Metamerism Ruler and Farnsworth-Munsell 100 Hue: significant colour shifts were associated with the different steps of recovery, and a constant difference finally remained between her two eyes, mainly due to the clearer replacement crystalline lens — whereas the other lens had naturally yellowed from daily exposure to the sun ultraviolet radiation.

This colorimetric approach of tissue trauma consequences particularly stroke me in a conference where visual perception was so essential. For further work, one could consider expressing the other visual parameters in such a quantitative way, so as to enable a precise follow-up: qualitatively described here, glare and distortion may (if possible) be respectively expressed in terms of optical Point Spread Function and Zernike polynomials. This complete characterisation, added to some well-known entoptic phenomena, could improve prevention and raise patient awareness during recovery.

Highlighted by Maëlle Vilber.

 

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