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Light comes in a wide variety. It is measured and described in various ways and we explain 12 of these characteristics and properties below.
How and where you light your totally hand painted oil on painting from Masterpiece Paintings Gallery will affect the viewing experience greatly which is why the painting may look very different than the digital photos we send you of your painting.
Luminous Flux is the light emitted in all directions by a lamp. It's measured in lumens (lm).
Luminous Intensity is the amount of luminous flux radiating in a particular direction. Luminous intensity is measured in candelas or candles (cd). The way the luminous intensity is distributed in space defines the radiant characteristics of lamps.
Luminance is the brightness of an illuminated or luminous surface as perceived by the human eye. It is measured in candelas/candles per unit area (cd/m2).
Illuminance is measured in lux (lx) and indicates the amount of luminous flux from a lamp falling on your painting. Illuminance is measured on horizontal and vertical planes.
Luminous Efficacy is the luminous flux of a lamp in relation to its power consumption and is a measure of economic efficiency. Luminous Efficacy is expressed in lumens per watt (lm/W). The higher the ratio of lm/W, the more light is produced from the power consumed.
Light Output Ratio is measured under controlled operating conditions and is the ratio of the radiant luminous flux of a luminaire to the luminous flux of the fitted lamp(s). It takes into account factors such as luminaire position and ambient temperature. It shows the percentage of luminous flux generated by the luminaire.
Reflectance indicates the percentage of luminous flux reflected by the surface of the painting. It is an important factor in calculating illuminance by the lumen method. Dark surfaces call for high illuminance while lighter surfaces require a lower level of illuminance to create the same impression of brightness.
Glare is bad news for oil paintings and often a problem for our photographers trying to accurately capture digital images of your reproduction painting. It impairs visual performance and causes discomfort. It can be created directly by the light source or indirectly by reflections on the shiny surface of your painting. Glare depends on the luminance and size of the light sources, its position in relation to the viewer, and the brightness of the surroundings and background.
Nominal Illuminance is the mean illuminance required for a furnished room from a lighting system of average age and condition. It depends on the visual tasks to be performed in the room and is measured in lx. On installation, illuminance should be 25% higher than the recommended nominal illuminance level because aging and soiling will deteriorate it.
Uniformity of illuminance or luminance is expressed as the ration of minimum to mean illuminance or luminance and is important in some applications. For paintings, you may find "wall-washers" superior to spotlights. However, halogen lamps give the best color rendering (1A) and come with a range of beams starting from 12 degrees wide. With the right beam you can cover the entire painting although the lumens drop drastically as the beam widens. At a certain distance a second lamp may be needed to achieve the appropriate amount of light.
Light Color describes the color appearance of a light source. It is characterized by the temperature K (Kelvin). Light color has a fundamental effect on the atmosphere created by a painting. There are three major groups of Light Color:
The Color Rendering Properties of a lamp is the effect the light source has on the appearance of your paintings. How well the light source renders the colors of your paintings is described by the Color Rendering Index Ra. The best rating is Ra = 100. The lower the index, the lower the quality of the color rendering.
A quality lamp dealer or a lamp manufacturer's catalog should provide the value for most of these properties for each lamp they offer to enable you to choose the right lamp to best display your paintings. Halogen lamps give the best color (1A) followed closely by deluxe warm white fluorescent (1A or 1B).