Péter Csuti

A New Concept of Color Fidelity for Museum Lighting

Abstract In almost all color rendering calculations, where a reference illuminant is needed, a Planckian or daylight spectrum of the same correlated color temperature as that of the test source is used (a few methods tried to use only D65 or a very restricted number of test illuminants, but these have not received general acceptance). In this article, a new calculation method of color fidelity is introduced that uses modern colorimetric practice in order to reproduce the colors of the painting as seen under the light under which it was painted (probably daylight for a picture prepared before the end of the 19th Century) but keeping the correlated color temperature of the light source warm-white for museum lighting. The principles of corresponding color color rendering are described and an Excel workbook is provided for further testing purposes.

Colour fidelity for picture gallery illumination, Part 1: Determining the optimum light-emitting diode spectrum

Colour rendering for picture gallery lighting means colour fidelity, showing the colours of the pictures as seen by the painter in the light he used in creating the pictures. As up to the beginning of the 20th century illuminance high enough for good colour vision was possible only in daylight, daylight would be the optimum illuminant. For art preservation and energy saving reasons this is not feasible. Museums often use light of 3500 K correlated colour temperature (CCT). A method is described that takes chromatic adaptation into consideration to determine the spectral power distribution producing least colour distortion of object colours while changing from a higher adaptation luminance at 6500 K to 3500 K illumination at a lower adaptation luminance. The method can be used for any CCT and adaptation luminance values.

Introduction to a study of preferred colour rendering of light sources

The European Union has financed a 3-year research project to establish optimal spectral power distributions of LED light sources for use in offices, commerce and homes. This paper summarizes the general questions relevant to colour preference investigations and introduces the investigations performed in the three laboratories that participated in the research. Subsequent papers will deal with details of the investigations and provide recommendations for optimum spectra in different indoor applications.

Colour fidelity for picture gallery illumination, Part 2: Test sample selection – museum tests

An earlier paper has described a new method to optimise the spectral power distribution of solid state lighting systems used in museums. This paper will discuss the question of the selection of the test samples used for the spectral power distribution optimisation for the illumination of renaissance paintings. For fine tuning the spectrum the help of museum curators was needed, who remember the appearance of the pictures under traditional light sources and who were able to advise lighting engineers to tune the spectrum to obtain a pleasing appearance. The paper will show the results obtained by testing the optimum spectrum in the museum. Part 1 of the present publication dealt with a new method to optimise the spectral power distribution of Solid State Lighting systems used in museums. Part 2 will discuss the question of test samples for the illumination of renaissance paintings and will show results obtained by testing the optimum spectrum in the museum.

“Gardener” Serious Game for Stroke Patients

This study introduces a serious game, “Gardener”, which is one of the games planned within the “StrokeBack” project. The aim of this game is to support the rehabilitation process of stroke patients with upper limb impairments and damaged psychomotor abilities.

Methods for correction of the LIDC by means of goniophotometers with rotating luminaires for different lamps

Goniophotometry is the fundamental measurement method for the measurement of spatial distribution of the light output of luminaires. The measurement results are represented by luminous intensity distribution curves (LIDC). This information is used by lighting designers for computation of photometric parameters to predict photometric values in real lighting installations. Therefore accuracy of the measurement of the LIDC is very important to provide the best information for other processing. In practice for this type of measurements various types of goniophotometers can be used according to recommendation CIE 121:1996. The main purpose of the recommendation is to describe the different types if goniophotometers and to give recommendations to the measurement process. Currently this document is under revision to implement the new approaches in the field of goniophotometry. One of the most common type of instruments is the goniophotometer with rotating luminaire. Due to the simplicity of construction, moderate space requirements and favourable price most of the testing laboratories are using this type of goniophotometer for measuring LIDC of luminaires. There are possible errors present due to work position of luminaire in Earth gravitation field is changing by rotating the luminaire around its axis. The CIE recommendation tells if this type of goniophotometer is used correction should be applied e.g. by means of auxiliary photometer or other possible methods. The auxiliary photometer during the actual measurement can shade luminous parts of the luminaire what can influence the shape of the LIDC and also the derived photometric results. This paper deals with investigation of the correction methods in goniophotometric measurements using luminaire rotating goniophotometers. Results of measurements of LIDCs were validated by means of other type of goniophotometer which did keep the work position of the luminaires (mirror goniophotometer) during measurements. Conclusions of this work should provide recommendation for methods of corrections in goniophotometry of LIDC of luminaires which LIDCs are measured with luminaire rotating type of goniophotometer. Furthermore paper reveals the possible errors which can occur in the measurement of LIDC of luminaires with various types of lamps.

Laboratory Measurement of Optical Properties of LEDs

Light-emitting diodes (LEDs) are solid-state sources, where the emitted light depends on the characteristics of the semiconductor material. It is usual to call an LED a light-emitting diode prepared from inorganic semiconductors, in contrast to organic light-emitting diode (OLEDs), prepared from organic compounds. In this chapter, devoted to the measurement of optical properties, we will deal only with inorganic semiconductor LEDs.