Second in a series of ?Light Papers? that address technical and aesthetic issues relating to the application of Matthews Designer Lighting in home theater environments.
Part Two Matthews Light Paper
Second in a series of "Light Papers" that address technical and aesthetic issues relating to the application of Matthews Designer Lighting in home theater environments.
Light Paper 1 established the premise that appropriate illumination is as essential to the home theater experience as is proper acoustical treatment. It also introduced four Matthews lighting instruments designed specifically for the home theater, and illustrated the application of those lighting instruments in four basic space layouts.
Light Paper 2 will provide an explanation of the quantitative and qualitative aspects of light that will allow the reader to expand his understanding of lighting beyond the basic space layout. In order to understand the material presented in Light Paper 2, it is necessary to first have an understanding of the material presented in Light Paper 1. Please also note that references to light Paper 1 will be made throughout this second
MATTHEWS DESIGNER LIGHTING
The task of lighting a space is manifest in the realization that lighting necessitates the preplanning of properly sized openings accurately located in walls, ceilings, and floors, serviced by electrical wiring runs to a central switching/dimming panel. While the designer is not expected to work without the assistance of mechanical and electrical contractors, the responsibility for the selection and placement of lighting instruments resides solely with the designer.
It is therefore necessary for designers to learn the characteristics and capabilities of various lighting instruments in order to assess their application in aesthetically defining a particular space. In a sense, the designer must selectively paint the space with light, employing individual or zone controlled lighting instruments to transform the space on queue into one of a number of desired motifs. The discipline requires pre-visualization coupled with adaptable lighting instruments.
1. Will the space be dedicated to home theater?
2. What other functions must the space serve?
3. How will the resulting space interface with the overall design and function of the home?
4. Are there limitations or obstructions within the space or an adjacent space that must be considered?
While it is understood that certain screens perform reasonably well in relatively bright environments, i.e., sports bars and family rooms, it will be assumed that the home theater space must be dark when used as a theater. How then, should the space appear with the lights up?
Because it is impossible to explore the almost limitless applications of home theater illumination in a single article, familiar reference points are presented to stimulate the visualization process. In order to simplify otherwise technical material, the method of presentation will offer basic formulas that can be solved quickly on site.
The standard measure of illumination is the foot-candle (fc). The chart below presents a condensed overview of several familiar settings and establishes a generally accepted illumination level for each.
In terms of interior illumination, 80 - 100 fc would best be described as a bright, functional space, while 30 - 40 fc is more in keeping with a relaxed, non-critical task area. In fact, intimate dining areas and subdued hotel corridors are often illuminated with no more than 10 fc of light.
Reflectance is not directly related to hue (color). The relationship of color and reflectance occurs when a color is tinted, toned or shaded. Tinting is accomplished by adding a measured amount of white pigment to a color to lighten its value. Likewise, toning is accomplished by adding gray pigment, and shading by adding black pigment. While tinting brightens the base color, both toning and shading subdue or darken the base color. In the vernacular of an artist, it should be noted that colors are rarely applied "out of the tube."
LIGHTING THE THEATER
The total lumen availability is used to determine the average illumination in a given area. The following formula is used to make the calculation on a flat surface such as a tabletop or floor area. The three applications described assume the use of a Matthews Cameo Light fitted with an MR-16 lamp as specified.
In simplified terms, the formula might be stated as follows: the average illumination on a surface - measured in foot-candles - is equal to the total lumens divided by the size of the area in square feet.
Using an FNV lamp rated at 875 total lumens to illuminate a table top in the theater measuring 42" square, the total foot candles (fc) measured at table top can be calculated as follows:
How bright is 71 fc? Recalling that 80 fc is typical for a living room, 71 fc is within the range of task illumination. Specific tasks that might be accomplished with 60 - 80 fc of illumination include handwriting and reading.
Suppose however, that we have a total of 875 lumens available to illuminate the entire 216 sq. ft. theater. The calculation is as follows:
Even if the intent is subtle illumination, 4 fc is probably below the threshold of acceptability.
Further, while a single lamp generating 875 lumens can effectively illuminate a 42" table, it is ineffective in terms of illuminating an entire room. The fact that the beam of the FDN lamp is capable of providing 71 fc of illumination on the surface of a 42" table, but only 4 fc in the overall room area, reveals an additional variable that must be understood.
Referring to Chart 1 again, you will note that the FNV has a beam angle of 55 degrees. For purposes of analysis, 71 fc is available at the 42" tabletop provided the beam angle of the lamp matches the area of the tabletop.
Referring to Chart 2, the 55-degree beam angle of the FNV lamp approximately covers the 42" tabletop at a distance of 36".
Should you decide to install a recessed light in a 9' high ceiling above the tabletop - assuming that the table stands 30" above the floor - the light must travel a distance of 108" - 30" = 78". Recalling that the 55 degree beam angle of the FNV lamp exactly illuminates the 42" table top at a distance of 36", if the recessed light is to be used, it will be necessary to recalculate the illumination, as the beam of the FNV lamp originally selected will cover an area of approximately 8' x 8' from a distance of 78".
Using the (E) Illumination formula, divide 875 lumens by 64 sq. ft. The result is only 14 fc from a distance of 78" as compared to 71 fc from a distance of 36".
In order to maintain 71 fc it will be necessary to select a light that can be lowered from the ceiling and installed at a height of 39" above the tabletop, or alternately by selecting a lamp with a narrower beam angle. The EXZ lamp projects a 27 degree beam that can be estimated to project a beam of approximately 3 1/2' in diameter at a distance of 78".
Using the (E) Illumination formula, divide 825 lumens by 12.25 sq. ft. The result is 67 fc, which is in range of the original illumination level.
Two additional factors must be recognized. Lamps are round and therefore project a round beam. When sq. ft. calculations are used, it is necessary to bear in mind that a square surface will experience a fall off in illumination at the corners.
Secondly, light beams do not perform in a predictable manner until they travel approximately ten times their diameter. Hence, the beam of a 2"- MR-16 lamp is best utilized at distances greater than 20".
To download a pdf file of this paper visit http://www.stjohngroup.com/newsdown.asp?fileid=5
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