ISO in photography refers to the International Organization for Standardization (ISO) standard that measures the sensitivity of a camera's image sensor to light. The ISO rating is a numerical value that indicates how sensitive the sensor is to light. The higher the ISO number, the more sensitive the camera is, which allows it to capture images in low-light conditions without requiring a slower shutter speed or a wider aperture. However, there's a trade-off: as you increase the ISO, the image quality may suffer from more digital noise or "grain." This noise is typically more pronounced in darker areas of the photo and can appear as random speckles or a gritty texture.
In film photography, ISO is determined by the type of film used. In digital photography, the camera's ISO can be adjusted to suit the lighting conditions. Here's a general breakdown of how ISO affects your photos:
- Low ISO values (e.g., ISO 100 or 200) are used in bright light conditions and result in low noise and high image quality.
- Medium ISO values (e.g., ISO 400 or 800) are suitable for moderate light conditions and provide a balance between noise and sensitivity.
- High ISO values (e.g., ISO 1600, 3200, 6400, or higher) are used in low-light conditions and can allow for faster shutter speeds and smaller apertures, but may introduce more noise in the image.
When selecting an ISO setting, photographers consider the available light, the desired depth of field, and the acceptable amount of noise for their specific shot. A common approach is to start with the lowest ISO possible to achieve the desired exposure, and then increase it as necessary while minimizing the noise. Modern digital cameras often have advanced noise reduction technologies that can help mitigate the negative effects of high ISO settings.