Relationship of EV To Lighting Conditions
The recommended f-number and exposure time for given lighting conditions and ISO speed are given by the exposure equation
where
- N is the relative aperture (f-number)
- t is the exposure time (“shutter speed”) in seconds
- L is the average scene luminance
- S is the ISO arithmetic speed
- K is the reflected-light meter calibration constant
Applied to the right-hand side of the exposure equation, exposure value is
Camera settings also can be determined from incident-light measurements, for which the exposure equation is
where
- E is the illuminance
- C is the incident-light meter calibration constant
In terms of exposure value, the right-hand side becomes
When applied to the left-hand side of the exposure equation, EV denotes actual combinations of camera settings; when applied to the right-hand side, EV denotes combinations of camera settings required to give the nominally “correct” exposure. The formal relationship of EV to luminance or illuminance has limitations. Although it usually works well for typical outdoor scenes in daylight, it is less applicable to scenes with highly atypical luminance distributions, such as city skylines at night. In such situations, the EV that will result in the best picture often is better determined by subjective evaluation of photographs than by formal consideration of luminance or illuminance.
For a given luminance and film speed, a greater EV results in less exposure, and for fixed exposure (i.e., fixed camera settings), a greater EV corresponds to greater luminance or illuminance.
Read more about this topic: Exposure Value
Famous quotes containing the words relationship, lighting and/or conditions:
“We think of religion as the symbolic expression of our highest moral ideals; we think of magic as a crude aggregate of superstitions. Religious belief seems to become mere superstitious credulity if we admit any relationship with magic. On the other hand our anthropological and ethnographical material makes it extremely difficult to separate the two fields.”
—Ernst Cassirer (1874–1945)
“Popular art is normally decried as vulgar by the cultivated people of its time; then it loses favor with its original audience as a new generation grows up; then it begins to merge into the softer lighting of “quaint,” and cultivated people become interested in it, and finally it begins to take on the archaic dignity of the primitive.”
—Northrop Frye (b. 1912)
“To get it right, be born with luck or else make it. Never give up. Get the knack of getting people to help you and also pitch in yourself. A little money helps, but what really gets it right is to never—I repeat—never under any conditions face the facts.”
—Ruth Gordon (1896–1985)