A7m3 can control door B with mobile phone.

The reason why a7m3 can control door B with mobile phone is because a7m3 camera has remote control function, which can be connected with the camera through mobile APP and operated by mobile phone. In this way, we can use the mobile phone to control various functions of the camera, including controlling the opening or closing of the camera door (door B).

This function of controlling camera door with mobile phone has certain popularization value in practical application. First of all, it increases the convenience and flexibility of users. Whether shooting a scene or in the case of remote control, we can control the camera at any time through the mobile phone without directly touching the camera itself.

Secondly, the function of controlling the camera door by mobile phone can also improve security. In some cases where scenes or equipment need to be protected, controlling the camera door through the mobile phone can reduce the need for direct contact with the camera and reduce the risk of being operated by unauthorized personnel.

In addition, the camera door controlled by mobile phone can provide more creativity and practicality. For example, when taking a selfie, we can control the camera door switch through the mobile phone to control the timing and angle of shooting, so as to obtain better shooting effect.

In a word, a7m3 camera can control door B through mobile phone. The realization of this function not only increases the convenience and flexibility of users, but also improves the security, which brings more creative and practical possibilities for shooting.