What is the sensitivity (ISO)
Sensitivity, as the name implies, is the speed at which the photosensitive element (CCD or CMOS) senses light.
In the film age, ISO sensitivity is an internationally unified index that measures the film speed standard used by traditional cameras. The sensitivity is determined by the film purchased. The value is fixed and is an attribute of the film itself. When buying film, the packaging will be marked with words such as ISO 100, ISO 200, and ISO400.
In the digital age, the sensitivity of electronic sensors can be set freely within a certain range, which is much more convenient than the original film era.
The sensitivity level is a multiple relationship, such as ISO100, 200, 400, 800, 1600... The sensitivity difference between adjacent ISOs is doubled, the larger the number, the higher the sensitivity.
With the current digital technology, we can say:
ISO800 (2017) or lower is low sensitivity
ISO800~6400 (2017) is medium sensitivity
ISO6400 (2017) or higher is high sensitivity
The effect of sensitivity
1. Raising the ISO can increase the exposure of the picture
The higher the ISO number, the more sensitive to light.
2. High sensitivity will cause noise problems
What is noise?
Noise, sometimes called noise, is mainly because the electronic image sensor (usually CCD or CMOS) receives light and converts it into electrical signal output process to produce tiny particles, and these particles are not available in the subject , Usually due to electronic interference.
How to avoid noise?
There are two situations where noise will occur. Usually, high sensitivity is used for shooting. In daily shooting, almost most of the noise is caused by the use of high sensitivity.
Another situation is long exposure. Digital cameras use electronic sensors instead of traditional film to image. Therefore, under long-term exposure, the electronic sensors will generate heat, and the increase in heat will affect the sensitivity of the sensor and cause noise on the screen. Therefore, consciously avoiding these two points can effectively reduce noise.