Pressing the shutter halfway focuses. What is one of the other things it does?

When you press the shutter button halfway, one of the primary functions is to engage the autofocus mechanism, but it also activates the camera's metering system. This allows the camera to assess the lighting conditions of the scene and display relevant settings on the viewfinder or LCD screen. This can include information such as shutter speed, aperture values, and ISO settings. Therefore, showing camera settings is a natural and useful function when preparing to take a photo, enabling the photographer to make informed adjustments based on what the camera recommends for optimal exposure.

While adjusting the ISO, aperture, or turning off the flash are important functions in photography, these actions typically require separate adjustments either manually by the photographer or by specific camera modes. The confirmation and display of camera settings upon pressing the shutter halfway serve as a helpful guide for photographers to preview and fine-tune their settings before capturing an image.