Commercial Photography Practice Exam

An f-stop change controls exposure in steps that halve or double the light entering the camera. Closing the aperture by one f-stop reduces the size of the opening, so about half as much light reaches the sensor. If the shutter speed and ISO stay the same, the image will be roughly one stop darker—in other words, exposure decreases by 50%. To maintain the same exposure after closing one stop, you’d need to open the aperture back up by one stop, lengthen the shutter, or raise the ISO.