Lesson 3 Quiz

Manual controls give the photographer authority over every exposure decision. Understanding aperture, shutter speed, and ISO as a system, rather than relying on automatic modes, is what separates intentional images from lucky ones.

The eye constantly shifts focus and suppresses peripheral clutter, but the camera records everything in the frame with equal fidelity. Recognizing this difference is what motivates careful framing and deliberate composition.

Film and sensors cannot adapt to the dark the way the eye's pupil and retina do. If the aperture, shutter speed and ISO are not changed for dim light, too little light reaches the film or sensor and the picture comes out very dark. That is underexposure, the opposite of overexposure.

Film and sensors record a narrower range of brightness than the eye can see at once. In a contrasty scene the darkest areas fall to black and the brightest blow out to white, so the contrast looks exaggerated. The eye adjusts as it looks around a scene, which is why the photo looks harsher than what you saw.

Shutter speed sets how long the sensor is exposed. A longer time lets in more light and lets moving things blur; a shorter time lets in less light and freezes movement. So it controls both light and motion.

At 1/2000 second the shutter is open for so short a time that moving subjects barely move across the sensor, so action is frozen sharply. The trade-off is less light, so the aperture or ISO usually has to make up for it.

The f-number is the focal length divided by the width of the opening, so a smaller number means a wider opening. A wider opening lets in more light and gives a shallower depth of field, with less of the scene in focus.

Aperture and shutter speed together set how much light reaches the sensor. If the combination lets in too much light the picture is too bright (overexposed); too little and it is too dark (underexposed). The camera does not fix a bad manual combination by itself.

Panning means following a moving subject with the camera while using a fairly slow shutter speed, such as 1/30 second. Because the camera moves with the subject, the subject stays fairly sharp while the still background streaks into a blur that shows speed. A fast shutter would freeze everything and lose that streaking.

In shutter priority mode (often marked S or Tv) you choose the shutter speed and the camera picks the aperture for a correct exposure. Aperture priority works the other way round: you set the aperture and the camera sets the shutter speed.