Chromatic Lighting and Environment: A Comprehensive Guide
Chromatic Lighting and Environment
To view objects, the wavelengths should be kept within the range of 380nm and 780nm. This is the wavelength range necessary to be perceived as light by the human eye and fall within the absolute threshold of visual perception.
In industrial hygiene studies, lighting highlights risks as a Physical Agent Risk. This is because it corresponds to a form of energy that propagates in the atmosphere and reaches humans. It is necessary to carry out relevant activities within the workplace with minimum allowable limits of lighting.
The DS.594 regulations mandate the existence of a minimum amount of lighting that must exist and be available in the workplace. This minimum is based on the activity that occurs in the workplace.
Types of Vision
Photopic or Day Vision:
Regulated by the rods and cones in the retina of the eye, allowing the perception of light and color differences.
Scotopic or Night Vision:
Regulated mainly by the rods of the retina, enabling the perception of differences in brightness, but not colors.
Mesopic or Intermediate Vision:
Also called twilight vision, this is a vision between photopic and scotopic. It has significant importance when designing lighting systems or signage in extreme visual conditions and considering their adaptations in the human eye.
Factors of Vision
Vision is a broad topic that involves several factors, divided into two categories: Psychophysiological Factors and Physiological Factors.
Psychophysiological Factors:
These factors involve the field of visual perception. There are very complex phenomena, some unexplained, such as the formation of colors from rotating gray segments on a white background.
Physiological Factors:
These are the most important factors related to industrial lighting and are divided into three categories: visual accommodation, visual adaptation, and visual acuity.
Visual Accommodation:
This is the ability of the eye to focus objects at different distances (near and far), producing a variation in the thickness and focal length of the lens (biconvex lens inside the eye). This increases the power of the lens, allowing you to see objects that are at a point close to the retina of the eye clearly. The time it takes to make a visual accommodation varies significantly with the age of individuals.
The need to see at different levels is closely related to muscular and postural comfort and the relaxation of the ciliary muscles, neck, etc.
Visual Adaptation:
This is the process where the eye adapts to different levels of brightness. The iris of the eye, which acts as the diaphragm of a camera, intervenes in this process, regulating the entry of light and adapting to the light spectrum that the eye is able to catch.
Visual Acuity:
This is the capability of the human eye to perceive and discriminate visually the smallest details, according to a certain scale and at a given distance (using charts with letters, numbers, and shapes).
Basic Illuminotechnical Concepts and Units
Luminous Flux:
The amount of light emitted by a light source, depending only on the properties of the source, also referred to as light output. Its measurement unit is the lumen, which is equivalent to the flux emitted in a unit solid angle by a light source of unit intensity (candela).
Luminous Efficacy:
This measures the amount of energy that becomes light in relation to the total energy consumed. It is a measure of the luminous efficacy of a source. Its unit of measurement is lumens per watt (lm/W).
Light Intensity (I):
The amount of light energy distributed evenly in a solid volume of space. As light power is a characteristic property of a light source, it provides information on the light flow at the origin.
Illumination or Illuminance (E):
The luminous flux incident on a surface. Its unit is the lux (lx), which equals one lumen of luminous flux incident on a surface of one square meter.
Luminance or Photometric Brightness (L):
The amount of light energy or light emitted or reflected from an illuminated object, making it visible. This should not only affect a certain level of lighting but also possess a contrasting difference between the object and the background color.
Lighting Contrast (C):
The luminance or brightness difference between an object and its background in relation to the luminance of the background itself.
Reflectance (r):
The ratio of light (luminance) reflected by a surface in relation to the light it receives.
Glare:
Occurs when the luminance relationships of objects in the visual field are very high, causing discomfort. For example, the headlights of a car at night.
Lamps
Incandescent (Bulb):
Light produced by the electrical heating of a wire, called a filament, to a temperature so high that the radiation falls within the visible spectrum. It consists of the following parts:
Filament:
Made of tungsten, which has a high melting point and a slow rate of evaporation, allowing for higher operating temperatures and greater efficiency. It is wound into a spiral shape inside the bulb, minimizing heat loss by conduction and convection. The incandescent lamp parts are divided into: 1) Filament, 2) Fill Gas, 3) Bulb, and 4) Cap.
Bulb:
A closed structure made of white, colored, or completely transparent glass that prevents the filament from coming into contact with outside air, whose oxygen would cause the filament to burn immediately. It is used to diffuse the light emitted by the filament inside the bulb.
Gas Fill:
An inert gas (nitrogen and argon) that increases the temperature at which the filament operates. The higher the pressure of the gas inside the bulb, the lower the evaporation of the filament, resulting in higher luminous efficiency and lamp life.
Cap:
The conductor that connects the filament to the lamp holder. Bayonet and screw caps are commonly used in general lighting. The metal components in its manufacture are brass, aluminum, and nickel.
Reflector lamps have a thin metal layer deposited on their inner surface that acts as a mirror, directing the light in a predetermined direction.
Halogen Lamps:
The high temperature of the filament in these lamps usually causes the evaporation of tungsten particles, leading to blackening. To prevent this, a halogen gas (iodine, chlorine, or bromine) is added, establishing a regeneration cycle that prevents blackening. The temperature is high enough to prevent condensation.
Imaging Lamps:
Their essential feature is a compact filament located at the exact position with regard to the cap, ensuring perfect alignment with the axis of the projector.
Lamps for Study and Theater:
These lamps have a highly concentrated filament to obtain the maximum light intensity within the produced beam. The filament is perfectly centered so you can replace the lamp without needing to adjust its focus.
Tubular Fluorescent Lamp (Low Pressure):
A low-pressure mercury discharge lamp where light is generated by fluorescent powders activated by ultraviolet discharge. It has a cylindrical tube shape with an electrode at each end, contains mercury vapor at low pressure, and a small amount of inert gas to facilitate ignition. The interior surface of the tube is covered with a fluorescent powder or phosphor, whose composition determines the color of the emitted light.