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A Curva de Kruithof

1941
  • Arie Andries Kruithof
Projeto de iluminação de escritório centrado no ser humano, ilustrando os princípios da Curva de Kruithof.

(Imagem gerada apenas para fins ilustrativos)

The Kruithof curve is an empirical graph from psychophysics that outlines a region of illuminance levels and color temperatures considered comfortable or pleasing. It postulates that at low light levels, humans prefer warmer color temperatures (more reddish/yellowish), while at high illuminance levels, cooler color temperatures (more bluish) are preferred. Lighting conditions outside this region may feel unnatural or unpleasant.

Arie Andries Kruithof conducted experiments in 1941 where observers were asked to evaluate the appearance of a room lit by discharge lamps of varying color temperatures and illuminance levels. By plotting the combinations that were rated as ‘pleasing’ or ‘natural’, he defined a bounded region on a graph with illuminance on the y-axis and temperatura de cor on the x-axis. For example, a dim light (e.g., 20 lux) was found pleasing only if it had a very warm color temperature (e.g., 2000 K), similar to candlelight. A bright light (e.g., 500 lux) was pleasing only if it had a cooler temperature (e.g., 4000 K or higher), similar to daylight.

While the original experiments had a small sample size and their strict validity has been debated, the general principle described by the Kruithof curve has been highly influential. It provides a simple, intuitive guideline for lighting design that aligns with human experience: the warm, dim light of a fire is cozy, while the cool, bright light of the sky is energizing. This concept is the foundation for modern human-centric and circadian lighting systems that aim to improve health and comfort by modulating light intensity and color temperature throughout the day.

UNESCO Nomenclature: 6114
– Psychology

Tipo

Empirical Model

Interrupção

Incremental

Uso

Nicho/Especializado

Precursores

  • Development of artificial lighting technologies with varying color properties
  • Early studies in psychophysics relating physical stimuli (light) to sensory perception (comfort)
  • Establishment of quantitative metrics for illuminance (lux) and color temperature (kelvin)

Aplicações

  • human-centric lighting design for offices and homes
  • tunable-white LED systems that mimic the day-night cycle (warm at night, cool during the day)
  • ergonomics of workspaces to improve productivity and well-being
  • interior design to create specific moods
  • user interface design for displays with adaptive color temperature (e.g., ‘night shift’ modes)

Patentes:

NA

Ideias de Inovação Potencial

  • an operating system that adjusts screen brightness and color temperature based on the Kruithof curve, not just time of day
  • automotive ambient lighting that dynamically follows the Kruithof curve based on exterior light levels
  • a smart lamp that uses a microphone to detect room activity levels and adjust its lighting along the Kruithof curve
  • hospital lighting systems that follow the curve to create a more calming environment for patients
  • cinema lighting that transitions along the curve as the house lights dim to improve visual comfort
  • vestível bio-sensors that adjust a personal lighting device based on the user’s stress level, using the curve as a baseline
  • virtual reality comfort modes that adhere to the Kruithof curve to reduce eye strain and simulation sickness
  • restaurant reservation systems that allow diners to choose a table based on preferred lighting profiles derived from the curve
  • e-reader displays that automatically adjust both frontlight intensity and color temperature to maintain a pleasing reading experience
  • smart home systems that learn a user’s personal preference curve, a variation of the original Kruithof curve
Related to: Kruithof curve, psychophysics, lighting design, visual comfort, illuminance, color temperature, human-centric lighting, ergonomics, tunable white, perception.

Contexto histórico

A Curva de Kruithof

1941
1986
1990
2000
1950
1990
1990

(Caso a data seja desconhecida ou irrelevante, por exemplo, "mecânica dos fluidos", é fornecida uma estimativa aproximada de seu surgimento notável)

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