The technology of ISO settings on digital cameras replicates the rated speeds of the films of yesteryear. In very general terms, ISO is the sensitivity to light of the sensor in the same way that film speeds were more or less sensitive to light. But there are differences between film and digital sensors; specifically, as the sensitivity setting increases on a digital camera, the output of the sensor is also amplified. This was referred to as grain when we used high-speed films. So, although you have the option of increasing the ISO sensitivity at any point in shooting, the tradeoff in increased amplification or the accumulation of an excessive charge on the pixels is an increase in digital noise. And the result of digital noise is an overall loss of resolution and image quality.
Partly because the 5D Mark II has relatively large pixels on the sensor and because Canon … Read More