Why can't you take a photograph of your image in a plane mirror and focus the camera on both your image and on the mirror frame?
it have different distance...your image is twice the distance as the mirror frame
When you try to take a photograph of yourself in a plane mirror and focus the camera on both your image and the mirror frame, you will face a challenge because of the nature of plane mirrors and how they form images.
To understand this, let's first clarify how plane mirrors work. A plane mirror reflects light rays in a way that the angle of incidence (the angle between the incident ray and the mirror surface) is equal to the angle of reflection (the angle between the reflected ray and the mirror surface). This creates the illusion of an image behind the mirror, which appears to be the same distance as the object is in front of the mirror.
Now, when you try to focus the camera on both your image and the mirror frame, you encounter two problems.
Firstly, the camera's autofocus system works by detecting contrast and sharpness. In a plane mirror, your image and the mirror frame are at the same distance from the camera, resulting in similar contrast and sharpness. Therefore, the autofocus will struggle to distinguish between the two and may not be able to focus correctly.
Secondly, when focusing on an object, the camera adjusts the lens position such that the light coming from that object converges to a sharp point on the camera sensor or film. In this case, if you focus on your mirror image, the light rays coming from your reflection have already converged at the plane of the mirror itself. Therefore, adjusting the lens position to focus on the mirror frame would require moving the lens backward to compensate for the increased distance. As a result, your image may lose focus or become blurry.
To overcome these issues, you need to choose a specific focal point - either your mirror image or the mirror frame - and focus exclusively on that point. This will allow the camera's autofocus system to detect contrast and sharpness properly and adjust the lens position accordingly.