However, because the digital camera is different from the ordinary camera, its photosensitive device uses CCD or CMOS, so there are corresponding requirements for the exposure, which also has the problem of high or low photosensitive sensitivity. This is equivalent to that the film has a certain sensitivity. In order to facilitate the understanding of digital camera users, digital camera manufacturers generally convert the sensitivity (or sensitivity to light) of the CCD of the digital camera into the sensitivity value of traditional film equivalently. Therefore, the digital camera has the term "equivalent sensitivity". For digital cameras, in fact, the film is not used, but the intensity of the incident light is sensed by the CCD or CMOS and related electronic circuits. In order to unify the measurement unit with the film used in traditional cameras, the concept of ISO sensitivity was introduced. Similarly, the ISO sensitivity of a digital camera also reflects its speed of light sensitivity.