Understanding Projection Terms
Distance from projector to screen: Known as “throw distance”, this is the actual measurement from the front edge of a projector lens to the projection screen surface. While it may be expressed in feet, it should be converted to inches for practical use. Farthest viewing distance: The actual measured distance between the center of the displayed image and the farthest possible viewer’s eye location.
Light level: The actual amount of light present in a room. Best measured by a light meter, it is expressed in LUX which is equal to 1 lumen per square meter. LUX: Equal to one lumen per square meter. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface.
Foot-Lamberts(fL): A foot-lambert equals 1/π or 0.3183 candela per square foot, or 3.426 candela per square meter.
LUX: Equal to one lumen per square meter Video format: Image size: The ratio between width and height The actual size of the display, typically of the displayed image. Expressed as expressed as the diagonal length, cornera fraction with the lowest common to-corner. denominator. (16:9 or 4:3) Lens ratio: The width of the image (W) relative to the throw distance (D) is known as the throw ratio (D/W). The most common projector throw ratio is 2.0. This means that for each foot of image width, the projector needs to be 2 feet away or D/W = 2/1 = 2.0.
Zoom range: The zoom range is the difference in magnification from one end of the zoom range to the other. Expressed as the lens ratio at shortest and longest extents of the zoom range. (1.39—2.09:1) 39
