Joint Lighting[✎ edit | edit source]
- Joint lighting is the simultaneous lighting of an area with both artificial light and daylight.
- This type of lighting is much more favorable than complete artificial lighting as it includes a number of the natural spectra of daylight.
- Even good artificial light is inadequate as a substitute for daylight.
- Joint lighting has the advantages of both day light (spectral composition, variability) and artificial light (adequate intensity).
- Obviously a higher concentration of daylighting than artificial lighting is preferable.
- Mixing ratio of daylight and artificial lighting should be at least 1:1. At a ratio of 1:5 and less, the test results differ very little from results obtained in artificial lighting only.
- Measurement and evaluation of the joint lighting is not easy. It consists of a constant component and a large amount of variability and spectral composition.
Glares (dazzles)[✎ edit | edit source]
- Difficulty seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night.
- Can be caused directly by a light source, or by its reflections on surfaces with a higher reflection factor.
- Glare is caused by a significant ratio of luminance between the task (that which is being looked at) and the glare source.
Types of Dazzles[✎ edit | edit source]
1. Dazzle by Critical Brightness
- Direct sunshine – the eyes cannot adapt and the person cannot see well.
- Critical value of brightness ranges from 200 000 to 1 000 cd.m−2.
2. Transitory Dazzle
- Due to sudden change of brightness, going from inside to bright outside. The eyes take some time to adapt.
- There is a sudden change in brightness of the visual field at a rate greater than 1:100.
3. Dazzle by Contrast
- When there are surfaces of various brightness. The eye cannot adapt to both and a dazzle occurs e.g. bulb fiber on wall.
Glare Reduction[✎ edit | edit source]
Glare can be reduced using a number of methods:
- Sunglasses – polarized sunglasses are designed to reduce glare caused by light reflected from surfaces such as water – used mostly by fly-fishers.
- Some cars include mirrors with automatic anti-glare functions.
- Anti-reflective treatment on eyeglasses reduces the glare at night
Links[✎ edit | edit source]
Related articles[✎ edit | edit source]
Bibliography[✎ edit | edit source]
- BENCKO, Vladimir, et al. Hygiene and epidemiology : selected chapters. 2. edition. Prague. 2008. ISBN 80-246-0793-X.