Resolution : A camera’s resolution capability is measured in megapixels. This measurement is based on the number of millions of pixels of image information that can be captured by the light-sensitive elements on the digital image sensor. Thus, a 15 megapixel camera is capable of capturing 15 million pixels of information.
ISO : Traditionally, the International Standards Organization (ISO) has provided a benchmark rating of the relative sensitivity of film. The higher the ISO rating, the more light sensitive a particular film is. Higher ISO films require less light to record an image. The ISO rating has been redefined for digital cameras, indicating the image sensor’s sensitivity to light. Most DSLRs have ISO settings from 100 to 3200 ISO. Unfortunately, at higher ISO settings (400 ISO and above), some cameras have difficulty maintaining consistent exposure for every single pixel in the image. To increase the sensitivity of the digital image sensor in these situations, the camera amplifies the voltage received from each image sensor element prior to converting the signal to a digital value. As the voltage signals from each element are amplified, so are anomalies within solid dark colors. This results in sporadic pixels with incorrect bright color values, also known as digital noise.