ISO in photography refers to the sensitivity of the cameras sensor or film to light. It is one of the three pillars of photography, along with shutter speed and aperture, and has a significant effect on the brightness or darkness of the image. ISO is measured as a numerical value, with a higher number indicating a higher sensitivity to light and a greater ability to capture light.

Here are some key points about ISO in photography:

• ISO is a standard set by the International Organization for Standardization (ISO) that represents sensitivity to light as a numerical value.
• ISO controls the amount of light that your camera lets in and has a huge impact on the darkness or light in your photos.
• Every camera has a range of ISO values, with the lowest number identified as the base ISO (usually around 100) .
• A lower ISO value means less sensitivity to light, while a higher ISO means more sensitivity.
• When you use low ISO values such as 300 and lower, generally the result is a higher quality photo.
• A higher ISO can be useful for increasing the shutter speed to freeze subjects in motion or to deepen the depth of field by narrowing the aperture.
• Noise that becomes more noticeable as the ISO sensitivity is increased can be reduced with the noise reduction function.

In summary, ISO is an important setting in photography that controls the sensitivity of the cameras sensor or film to light. It can be used to adjust the brightness or darkness of the image and can be adjusted to suit different lighting conditions and creative needs.