ISO stands for International Organization for Standardization and is used for digital cameras and is a measure of the sensitivity of the camera’s sensor to light. Smaller values represent less sensitivity and larger values represent more sensitive. Doubling or halving your ISO produces an increase or decrease of 1 stop of exposure. Increasing the ISO will result in more noise and result in poorer quality photographs.
What is the best ISO to use for bird photography? The lower the better, but anywhere between 100 and 10,000. For example, low ISOs are typically used when you have plenty of natural lighting (e.g., shorebirds along a beach) and high ISOs are typically used in low light (e.g., photographing Ttinamous in a triple canopy jungle). High ISOs are also used if you have very short exposures (e.g., freezing a hummingbird’s wings). Recall, that the photographs with high ISOs will result in photographs with significant noise. Some of the noise can be removed during post processing as shown by comparing these photographs.