Color Characteristics of Lamps

Color characteristics of lamps.

Color perception is a general, subjective feeling that a person experiences when looking at a light source. Light can be perceived as warm white, neutral white, or cool white. The objective impression of a light source’s color is determined by color temperature. Light chromaticity is the temperature of a black body at which it emits radiation with the same chromaticity as the radiation in question. In other words, it is a measure of the objective impression of a given light source’s color. If the temperature of the “black body” increases, the blue component in the spectrum increases, while the red component decreases. The main color temperature indicators for fluorescent lamps are as follows (unit: Kelvin K):

• Super-warm white – 2700 K;

• Warm white – 3000 K;

• Natural white (or simply white) – 4000 K;

• Cool white (daylight) – over 5000 K.

Regarding color temperature, lamps with a low temperature (<5000K) impart a reddish tint, while lamps with a high color temperature (>5000K) highlight green well. For example, at a color temperature of less than 5000K, the light is poor because it has a yellow tint, whereas light at 10000K is whitish and colors become bluish. Under light of less than 5000K, aquatic plants have a yellow tint and look unhealthy. Under 10000K light, aquatic plants become too green and look artificial.

Thus, when choosing lamps by color temperature “K” so that underwater plants look natural, you need to choose lamps with a color temperature of 7000-8000K. Lamps with a low color temperature K<5400 promote algae growth. As for fluorescent lamps, “warm” (3300K) and “cool” (4000K) do not reproduce the temperature of natural daylight and provide too much green light, but too little red and blue light for plant growth. There are much more advanced T5 “daylight” lamps (5400-8000K) whose light temperature is close to solar.

Another significant characteristic to pay attention to (especially in professional lighting) is the color rendering of a fluorescent lamp. The color rendering accuracy of a certain lamp shows us how natural our environment looks in the light of this lamp. Color rendering ability is reflected by the CRI (Color Rendering Index, Ra) or Color Rendering Index (CRI). CRI is often indicated in catalogs as Ra. The maximum is 100 – this is the value of many incandescent lamps and sunlight.

Fluorescent lamps with the same color temperature value can have different color rendering, which must be taken into account. The reason for the difference may lie in the different spectral composition of the light they produce. CRI measures how accurately a light source conveys the true color of objects. An ideal light source would have CRI=100. Lower values mean that colors are shifted from their true hue and saturation: for example, under yellow light, yellow stripes will be less visible; under blue, blue ones. Each lighting manufacturer marks their products according to their own special type, but these designations can be deciphered to obtain necessary information about the lamp. For comparison, 8 basic colors (Ra-8) are usually chosen and averaged.

Spectral intensity distributions

The resulting value is denoted by the symbol Ra and taken as the CRI – the lower this value, the poorer the color rendering. From 91 to 100 is considered very good color rendering, 81-91 as good, 51-80 as medium color rendering, less than 51 as weak color rendering. Lamps with a high CRI>90 are designed for installation where very accurate color perception is important – in printing houses, graphic studios, museums. If you have lamps with an RA parameter from 80 to 90, they have a good spectral light component, and with an RA value greater than 90, lamps have a very good, one might say ideal, frequency spectrum. Try to use lamps with a high CRI value to make your plants look more attractive.

These two parameters are usually indicated on the labeling of fluorescent lamps. For example, /735 means a lamp with CRI=70-75, CCT=3500K is a warm-white lamp, /960 is a lamp with CRI=90, CCT=6000K is a daylight lamp. You should choose tri-phosphor fluorescent lamps with maximum CRI so that color distortions of the underwater world are minimal (with a color temperature of 5400 – 10000K). All new-type T5 fluorescent lamps are tri-phosphor and have a CRI of at least 80.

Luminous efficacy depends on the length of the lamp. As seen from the graph, it makes sense to use, for example, one 40 W lamp instead of two 20 W lamps. The color of the lamp in the designation usually stands after the / sign. For example, F18/43. Colors are designated either by a letter combination (/CW, etc.) or numbers. The color is set by the color temperature value (CCT). For standard lamps with a low color rendering index (CRI), the color is designated as two digits:

Lamps marked with a three-digit code contain information regarding the quality of light (color rendering index and color temperature). The first digit is the color rendering index in 1×10 Ra (compact fluorescent lamps have 60-98 Ra, thus, the higher the index, the more accurate the color rendering). The second and third digits indicate the color temperature of the lamp. Thus, the marking “827” indicates a color rendering index of 80 Ra and a color temperature of 2700 K.

Code — Features and visual perception of lamp light.

530 — Warm tones light with poor color rendering.

640/740 — “Cool” light with mediocre color rendering and luminous efficacy.

765 — Bluish “daylight” with mediocre color rendering and luminous efficacy.

827 — Similar to incandescent lamp light with good color rendering and luminous efficacy.

830 — Similar to halogen lamp light with good color rendering and luminous efficacy.

840 — White light for work surfaces with very good color rendering and luminous efficacy.

865 — “Daylight” with good color rendering and mediocre luminous efficacy.

880 — “Daylight” with good color rendering.

930 — “Warm” light with excellent color rendering and poor luminous efficacy.

940 — “Cool” light with excellent color rendering and mediocre luminous efficacy.

954, 965 — “Daylight” with a continuous color rendering spectrum and mediocre luminous efficacy.

Lumens and lux are often a source of confusion. These quantities are units of measurement of luminous flux and illuminance, which need to be distinguished. A lumen is a unit of luminous flux, i.e., emitted light. A lux is a unit of illuminance, i.e., received light. Luminous flux characterizes a light source, while illuminance characterizes the surface upon which light falls. Illuminance is measured in lux (lx). A light source with a luminous flux of 1 lm uniformly illuminating a surface of 1 sq. m creates an illuminance of 1 lx on it. The electrical power of a lamp is measured in watts (W), while luminous flux (“light power”) is measured in lumens (lm). The more lumens, the more light the lamp gives. Instruments for measuring illuminance are called luxmeters. Lighting color is measured in Kelvin degrees.

Lamp manufacturers indicate luminous flux in lumens (i.e., this is the total luminous flux from a given lamp), but how applicable is this for aquariums? Not at all. This value shows how bright the lamp appears to the human eye, and nothing more. Since the human eye is not equally sensitive to different areas of the spectrum, this does not indicate the “real” brightness of the lamp at all. Human eye sensitivity is at its maximum at a wavelength of 555 nm (green color). Therefore, lamps whose main emission spectrum is shifted towards the red or blue side will seem less bright to us. Hence the conclusion – if one lamp is said to give more lumens than another, it does not mean it shines brighter; it just appears brighter.

The luminous flux emitted by a lamp strongly depends on the ambient air temperature. The lumen values specified in catalogs are measured at an ambient air temperature of 25°C. The use of various reflectors can sharply increase the temperature of the air surrounding the bulb and reduce the luminous flux by 10-15%. Therefore, the luminaires used must have ventilation holes to lower the lamp temperature.

Recommendations for duration and selection of light sources.

Aquarium lighting characteristics. Spectral composition of lamp light.