b.Hold meter about 15cm from the subject, point Lumigrid to each surface of the subject and read the footcandle scale value.
c.To determine the luminance range, it is sufficient to divide the highest meter indication by the lowest. For example, if the highest value is 80 and the lowest 5, the luminance range becomes 80/5 = 16/1 or 16 : 1.
Luminance range measurement
3.To obtain superior color photographs, determine upper and lower limits.
a.Adequate color photographs can be obtained with typical color film if within the subject luminance distribution, the maximum is less than 4 times the center point and minimum more than 1 /4 times (i.e.: overall luminance range becomes less than 16 : 1).
b.With a luminance center point of 20, if the measured maximum luminance is higher than 80 (center point 20 x 4 = 80), color of that surface will become faded in the photograph. Consequently, a slight reduction of incident light to this portion becomes required.
c.Conversely, a portion with a measured minimum luminance less than 5 (center point 20 / 4 = 5) requires increased illumination in order to obtain an acceptable color photograph.
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