noun
: a system of photographic diaphragm or stop marking in which the numbers are proportional to the intensities of the light permitted to pass and hence to the times required for exposure
noun
: a system of photographic diaphragm or stop marking in which the numbers are proportional to the intensities of the light permitted to pass and hence to the times required for exposure
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012