Colour Memory Analysis for Selected Associative Colours

Colours are one of the most important factors in everyday life. The exact number of existing colours is not yet fully known. Nevertheless, people are known for having poor colour memory. The ability to remember colours depends both on the characteristics of an individual and the situation in which the colour needs to be recalled. The field of colour memory (perception and memory of unusual colours) has been very poorly researched. The aim of this study was to analyse long-term colour memory for selected associative colours, comparing it with short-term colour memory. The research approach was based on observation, with observers observing for a period of time a particular colour, image, or a descriptively given reference colour. Colour was treated separately from associations in the first part, and related to associations in the second and third parts. The first part contained all the reference colours shown independently of associations, the second part contained grayscale images of brands, and the third part comprised descriptively given colours. The result analysis showed that people remember colours very poorly. Observers generally performed better in testing short-term memory. Moreover, the way the template was presented had a noticeable effect on the long-term colour memory. When the image was given in grey, the results were better. The descriptive rendering of reference colours shown did not contribute to better results. The gender of observers did not significantly affect the results

Study of Ink Jet Print Resistance Using Various Colour Difference Formulas

Three frequently used formulas and their power function modifications were used to calculate the colour differences after the exposure to light and to study the stability of ink jet prints by spectrophotometric measurements. The prints were exposed to the simulated daylight of different spectral composition at constant conditions of temperature and relative humidity. According to the results, the black prints were the least affected and the magenta prints exhibited the biggest colour differences. The most resistant have proven to be the prints on archival paper which contained no optical brightening agents. The presence of shortwave radiation between 320 and 300 nm additionally diminished the resistance of prints. The same conclusions were obtained regardless of the colour difference formula applied, with one exception. Generally, the CIEDE2000 formula performed the best, especially when comparing samples with a smaller colour difference

Impact of protective glass on photodegradation of ink-jet printed documents

Ink-jet printing has recently been increasingly used for professional and domestic purposes. However, the degradation of ink-jet prints under the influence of external factors, predominantly light, can cause unexpected problems and lead to the limited life span of a product. It is therefore essential to have in-depth knowledge about the materials, i.e. paper and ink, used for ink-jet printing and to consider their lightfastness to assure the resistance of a print as a whole. The aim of the present research was to study the lightfastness of ink-jet prints protected with glass. Using a printer with dye-based inks, samples of cyan, magenta, yellow and black were printed on different paper substrates. Prints and substrates alone were exposed to the radiation of xenon light for a limited time to simulate the action of average daylight. Some of the samples were exposed to radiation without protection, while others were covered with ordinary window glass or glass which ensured UV protection. Afterwards, the changes on samples were evaluated spectrophotometrically and colour differences were calculated using the CIEDE2000 equation. The results showed that glass effectively reduces the photodegradation of ink-jet prints. Protection with UV glass proved to be more effective than with ordinary glass. The substrate selection was also significant in achieving print lightfastness, as much smaller colour differences were observed on the prints made on photo paper than on those printed on plain office paper

Fastness of dye-based ink-jet printing inks in aqueous solution in the presence and absence of oxygen

Photodegradation of the ink-jet prints is a complex process in which many external and internal factors are involved. Nevertheless, the role of colorants and various accompanying substances in the ink is often overlooked. Our research work aimed to determine the fastness of water-based ink-jet inks in aqueous solutions. A printing ink often contains a complex mixture of colorants to achieve optimal optical properties of color and a suitable fastness of the print. Therefore, we investigated the composition and stability of cyan, magenta, yellow, and black inks under the influence of UVC light in the presence of oxygen as well as in an inert environment based on TLC chromatography and spectrophotometric analysis. The process of photodegradation was evaluated based on ink amount and half-life. According to the results, the majority of inks consist of at least two colorants that differ in color and polarity. The results have shown that the presence of oxygen negatively affects the stability of inkstherefore, the inert atmosphere prolongs the durability of ink in water solution

Una verificación empírica de la mejora de la fórmula de diferencia de color CIEDE2000 respecto a CIELAB

Los 10 pares de muestras elaborados en 2002 por el Dr. Alman, con la finalidad de mostrar la mejora de CIEDE2000 con respecto a CIELAB, están diseñados muy cuidadosamente: Los pares 1, 2 y 3 muestran la utilidad de la corrección de claridad, el par 4 la de la corrección de croma, los pares 5 y 6 la de la corrección de tono, los pares 7 y 8 la del término de rotación, y los pares 9 y 10 la de la corrección de grises. Los resultados de las fases 1 y 2 de nuestro experimento visual son bastante similares: utilizando el índice STRESS, la predicción de los mismos mediante CIEDE2000 es considerablemente mejor que la realizada por CIELAB. Los resultados logrados por CIEDE2000 en la predicción de la fase 2 de nuestro experimento son muy similares a la variabilidad inter observador, medida también mediante STRESS. La variabilidad intra-observador es ligeramente superior a la inter-observador.Ministerio de Educación y Ciencia, Proyecto FIS2007-64266, cofinanciado con fondos FEDER (UE)