ISO sensitivity is the ability of a sensor to provide a defined
response for a given level of lighting. Photographers use this
information to determine the nominal exposure conditions. If the
actual ISO sensitivity of a digital camera’s sensor is lower
than the sensitivity set by the user, the image is underexposed;
if the sensitivity is greater, the image is overexposed. To be
easily understood by photographers, the ISO sensitivity of
digital cameras has been defined such that it is similar to the
ISO sensitivity of photographic film cameras, thus lower
sensitivities require longer exposure for the same luminance to
produce the same result. However, just as very sensitive films
are known to be very grainy, parallels can be drawn for digital
cameras, since high sensitivities are related to high gain and
noise amplification. While it is a common practice for camera
vendors to emphasize high ISO settings on their cameras, it must
be said that high ISO does not mean good image quality. Any
serious photographer k