What does camera iso mean?

Camera ISO is the sensitivity. Sensitivity is a measure of the sensitivity of negative film to light, which is determined by sensitivity measurement and several values measurement. The ISO standard is ISO 6. Films that are less sensitive to light need to be exposed for a longer time to achieve the same imaging effect as photosensitive films, so they are usually called slow films.

Highly sensitive negatives are therefore called fast negatives. ISO system closely related to sensitivity is used to measure the sensitivity of digital imaging system. Whether it is digital or negative photography, using higher sensitivity to reduce exposure time usually leads to the decline of image quality (due to thicker negative particles or higher image noise or other factors).

The working principle of ISO

The ISO sensitivity means that if you choose a higher ISO sensitivity under the same EV exposure value, you can get the same exposure with a faster shutter speed under the same aperture. On the contrary, a smaller aperture can be used to maintain correct exposure without changing the shutter.

Therefore, when shooting in dim light, you can often choose a higher ISO sensitivity. Of course, for SLR cameras, you can also choose to use a larger caliber lens to improve the luminous flux. For ordinary digital cameras, because they use a fixed lens, only by improving the ISO sensitivity can they adapt to shooting in dim light, especially when auxiliary light cannot be used.