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Exposure value is a base-2 logarithmic scale defined by (Ray 2000, 318): where. N is the f-number. t is the exposure time ("shutter speed") in seconds [2] EV 0 corresponds to an exposure time of 1 s and an aperture of f/1.0. If the EV is known, it can be used to select combinations of exposure time and f-number, as shown in Table 1.
On a sunny day with ISO 400 film / setting and aperture at f /16, set shutter speed to 1 / 400 or 1 / 500 . As with other light readings, shutter speed can be changed as long as the f-number is altered to compensate, e.g. 1 / 250 second at f /11 gives equivalent exposure to 1 / 125 second at f /16.
An approximately correct exposure will be obtained on a sunny day using ISO 100 film, an aperture of f /16 and a shutter speed of 1/100 of a second. This is called the sunny 16 rule: at an aperture of f /16 on a sunny day, a suitable shutter speed will be one over the film speed (or closest equivalent).
A shutter speed of 1 ⁄ 50 s with an f /4 aperture gives the same exposure value as a 1 ⁄ 100 s shutter speed with an f /2.8 aperture, and also the same exposure value as a 1 ⁄ 200 s shutter speed with an f /2 aperture, or 1 ⁄ 25 s at f /5.6. [citation needed]
For example, an EV of 10 may be achieved with an aperture of f / 2.8 and a shutter speed of 1/125 s. The same exposure is achieved by doubling the aperture area to f / 2 and halving the exposure time to 1/250 s, or by halving the aperture area to f / 4 and doubling the exposure time to 1/60 s; in each case the response of the film is expected ...
An example of the use of f-numbers in photography is the sunny 16 rule: an approximately correct exposure will be obtained on a sunny day by using an aperture of f /16 and the shutter speed closest to the reciprocal of the ISO speed of the film; for example, using ISO 200 film, an aperture of f /16 and a shutter speed of 1 ⁄ 200 second. The f ...
Long-exposure photograph of a break in pool. Long-exposure, time-exposure, or slow-shutter photography involves using a long-duration shutter speed to sharply capture the stationary elements of images while blurring, smearing, or obscuring the moving elements. Long-exposure photography captures one element that conventional photography does not ...
The ISO arithmetic speed has a useful property for photographers without the equipment for taking a metered light reading. Correct exposure will usually be achieved for a frontlighted scene in bright sun if the aperture of the lens is set to f/16 and the shutter speed is the reciprocal of the ISO film speed (e.g. 1/100 second for 100 ISO film).