Papers by Keyword: Color Temperature

Abstract: Balancing thermal comfort and energy efficiency in buildings remains a key challenge. While HVAC systems regulate temperature directly, recent studies suggest that visual factors—such as horizontal illuminance and correlated color temperature (CCT)—can influence perceived thermal comfort through psychological mechanisms. This study examined how these visual factors affect thermal sensation and comfort in cooling environments (26–30°C). A controlled climate chamber experiment was conducted with 54 healthy female participants under varying air temperatures, illuminance levels (100–2900 lx), and CCTs (2800–5200 K). Mean skin temperature increased with air temperature but remained unaffected by variations in illuminance or CCT, indicating stable physiological responses to visual conditions. However, higher illuminance and CCT levels led to enhanced sensations of coolness, particularly at 30°C. Visual comfort also improved slightly with increasing illuminance, while CCT effects on comfort were modest and dependent on air temperature. These findings suggest that adjusting the visual environment can enhance thermal comfort without changing actual temperatures, supporting higher cooling setpoints (around 28°C) and contributing to energy-efficient building design.

Abstract: The majority of energy consumption in buildings is attributed to air conditioning and lighting systems. To address environmental concerns and reduce energy consumption, minimizing the energy usage associated with these systems is imperative. This study investigates the impact of LED lighting's illuminance and correlated color temperature changes on psychological evaluations in indoor settings. The research aims to contribute to sustainable building design by enhancing energy efficiency through lighting design. Furthermore, it aims to validate the Kruithof curve in LED lighting. The experiment, conducted in the summer of 2023, involved 17 female students experiencing various lighting conditions in a controlled environment. Illuminance levels ranged from 100 to 3000 lx, and color temperatures ranged from 2800 to 5200 K. Using a 7-point impression evaluation (SD method) with 20 pairs of adjectives, three factors ("Comfort," "Cleanliness," "Dynamism") were identified to explain variations in evaluations. A strong positive correlation was found between "Comfort" and color temperature. Comparison with Kruithof's experiment revealed different trends, with "Comfort" scores being positive at specific color temperatures above a certain illuminance level.

Abstract: In order to investigate the influence of the light source with different illuminance and color temperature on the observers’ visual performance, five kinds of light sources were selected, named LED1, LED2, LED3, LED4 and Fluorescent, which have different illuminance or color temperature. 3 series of visual experiments, such as the ‘find out’ experiment, compared experiment, dose experiment were designed.13 observers were organized to carry out the experiment in the given time in turn. The reading rate, accuracy , index of mental capacity (IMC) and visual comfortable level score were analyzed, the results indicated that the light source with the lower color temperature and medium illuminance has the best visual performance and comfortable visual feel.

Abstract: In order to study the LED light source illumination and the correlated color temperature effect on the human eye visual performance and physiological changes, through the comparative experiments of visual task performances under the different color temperature (3000K low color temperature, 4000K intermediate color temperature) and the different illumination (1145lux high intensity, 500lux middle intensity, 288lux low illumination), study the relationship between the biological effect and visual performance from two aspects of the visual perception performance and the physical efficiency such as blood pressure and pulse. Research indicates that color temperature 3000K or 4000K, intensity of illumination in about 500lux LED light source is suitable to visual task.

Abstract: Automatic white balance algorithm (AWB) is significant for color temperature restoration of digital imaging system. According to the limitations and disadvantages of existing traditional white balance methods, in this paper a new AWB algorithm for airborne camera is proposed. Using RGB and histogram information divide the input image into different color character regions; according to the color richness level, adopt different white balance algorithms to achieve chromatic aberration adjustment. Experiment results show the effectiveness of the proposed AWB algorithm for airborne camera.

Abstract: This paper is mainly about the high power LED temperature characteristics. With the integrating sphere, we conduct an experiment to observe and analysis the relationships of temperature and color coordinates, peak wavelength, color temperature, forward voltage, peak bandwidth, color purity, electric power. Finally we get that the temperature is the main factor to affect the color performance of white LED photoelectric, with the white LED apparent temperature rise, forward voltage, the color coordinates and color purity tends to go down. On the contrary with increasing junction temperature, the half-value wavelength and color temperature are increased accordingly.

Abstract: The application of LED was in an exploring stage, while it had a series of problems on architectural lighting, such as light distribution, color temperature selection and light attenuation. Based on the relations between color temperature and visual effect, this thesis discussed the relations between three kinds of LED color temperature and the changes of human pupil size. In the circumstances of settled lighting conditions, adjust visual regional background brightness, the changes of pupil size was measured with the aid of iView eye tracker. The survey finds that the pupil shrinks with the high rise of light source color temperature, which leads to the improvement of visual efficiency. However, high color temperature appears dazzling, which is likely to cause fatigue and discomfort.

Abstract: The white balance is an important parameter of digital camera which makes a great impact on the application of digital cameras. However, due to the limitations of hardware of digital camera, the output image of digital camera cannot restore true colors of the objects under the different light sources conditions. And existing automatic white balance (AWB) algorithms have many application restrictions, particularly the single color image, the algorithms always failure to adjust. To solve this problem, this paper proposes an optimized algorithm based on the gray world assumption and HSI color model. According to the R, G and B color components probability distribution, the algorithm adjusts the image by using the difference value of color. Experimental results show that our algorithm can adjust images in complex situations; meanwhile these confirm that this method is not only effective, but also has the advantage of easy realization.

Abstract: Under A, CWF, D55, D65, D75 five different illuminants, color differences of 53 natural oval Jadeite-jade with fine texture are analyzed, which color is yellow-green to dark green. All 5 tested lighting sources were compared based on the uniform color space CIE 1976L*a*b*. Jadeite-jade’s lightness L* is increasing when color temperatures of five different standard illuminants increase, and it can reach the very top of 45.72 under D75, so it appears brighter and lighter than any other illuminants and it influences the appraisal of the samples’ color. The spectrum power distribution of D75, D65 and D55 reveal the strong radiant energy in the range from 500 to 570nm, so consequently the color coordinates a*, b* and chroma C* is higher than the other two illuminants. But samples’ lightness and chroma under D55 are weaker compared to D65 and the color under D55 is dark. Meanwhile, D65 stands for the average daylight and color under D65 close to the true color of samples. Because of weakest radiant energy in the range from 500 to 540nm (green area) and strongest radiant energy in the range from 540 to 570nm (orange area) in CWF’s spectrum power distribution, the absolute value of a*=14.01 is lowest and b*=12.93 is highest under CWF, so samples’ color under CWF is green with a yellow tint. The maximum hue angle h0 is 150.42 under A, and the absolute value of a* is higher than that under CWF, so it shows stronger green tone than CWF. It is concluded that D65 is preferred to be ideal illuminants for the evaluation of jadeite-jade color green especially compared with other 4 illuminants.