SkillsUSA Photography Practice Exam

When you press the shutter button halfway, the camera’s exposure metering kicks in in addition to autofocus. The light meter measures the amount of light in the scene through the lens (TTL metering) and uses that reading to help set a proper exposure. This tells the camera how bright or dark the scene is so it can choose an appropriate combination of aperture and shutter speed (and ISO if needed) to avoid underexposure or overexposure.

Flash activation isn’t triggered by a half-press—that typically requires a full press or a separate flash setting. Starting video and adjusting white balance aren’t tasks tied to the half-press in the normal workflow; they’re controlled by other buttons or menu settings. So measuring the light, i.e., metering for exposure, is the function that occurs along with focusing when you half-press.