The angle of view changes significantly when shooting with Continuous Auto Focus (AF-C).
To downsize the lens in the camera, the focus lens is placed just in front of the image sensor.
This makes the variation of the angle of view, caused by movement of the focus lens, wider than in previous cameras. This produces a wider variation in the image displayed on the monitor while pressing the shutter button halfway down.
In addition, depth of field increases, especially, when the aperture value (F-value) is higher. For this reason, the focus lens needs to be moved wider during the contrast peak detection. In this condition, the variation of the angle of the view tends to be more pronounced.
However, the movement of the focus lens and the consequent variation of the angle of view on the monitor are caused by the movement when trying to focus on the subject. This means that issues such as focus shift on the recorded images do not occur.