Light intensity tends to dim with distance. For a
point source of light, intensity decreases as distance increases. Intensity (
I) is inversely proportional to the square of the distance (
D), as expressed by the formula . For a point
light source, with a tiny area, intensity is inversely proportional to distance. A softer light source is larger in area and so does not drop in intensity as quickly as a point light source does. Certain lensed lighting instruments (such as
ellipsoidal reflector spotlights) have a good deal of "throw" and do not lose much intensity as distance increases. The nearly parallel rays of such instruments tends to cast hard shadows. These light sources tend to be more effective at long distances than soft light sources. ==Softness/hardness of various light sources==