Larger f-stops, such as f/11, will require slower shutter speeds or more light and produce images with larger depths of field (more of the scene is in focus). Smaller f-stops, such as f/4, will allow faster shutter speeds or less light and produce images with shallower depths of field (less of the scene is in focus).

Does f-stop change focus?

They don't change while focusing — they stay wide open until right before the shutter is released. That is definitely not the case, especially with the camera and lens mentioned. The aperture iris does not change in manual or AP mode.

Does aperture affect focus?

The lens aperture plays two roles, controlling both focus and exposure: First, it adjusts the depth of field in a scene, measured in inches, feet or meters. This is the range of distance over which the image is not unacceptably less sharp than the sharpest part of the image.