- FOCAL LENGTH VERSUS ANGLE OF VIEW: Focal length is the distance between the optical center of the lens and the image sensor when the lens is focused to infinity. By itself focal length does not indicate how much of a subject is visible in the viewfinder. How much you see is affected by the angle of view, which depends on the focal length and the size of the image sensor. Long focal length lenses (telephotos), such as a 300mm “35mm equivalent focal length,” have a narrow angle of view and magnify the subject within the viewing area. To capture a wider angle of view, you need a wide-angle lens (or shorter focal length).
- TWO MAXIMUM APERTURES PER LENS?: Zoom lenses have two maximum apertures. While that may not make sense at first, here is why it does. Let’s consider a 18-55mm f/3.5-5.6 lens for example. When you have the lens at maximum wide angle (18mm), it has a maximum aperture of f/3.5. When you zoom all the way to 55mm, the maximum amount of light that the lens allows drops to f/5.6, or less than half of the first setting. Each maximum is conditional, based on the level of zoom.
- SHUTTER SPEED: You can begin to freeze most sports and performing arts action at shutter speeds as low as 1/320, however 1/500 to 1/800 may be needed. Depending on your relative position and distance to the action being photographed, you will need a faster or slower shutter speed. Freezing motion is hardest when the subject travels perpendicular to you and is close. A slower shutter speed can accomplish the same “freeze frame” if the action is moving to or away from you and is at a distance.
- CONTROLLING DEPTH OF FIELD: There are three contributors to Depth of Field (DoF). The first is aperture setting. Wider apertures (lower f stop numbers) have less DoF than smaller apertures (larger f stop numbers.) Moving farther from your subject increases DoF, while moving closer decreases DoF, all other settings remaining equal. Wide angle lenses have greater DoF than telephoto lenses.
- PERSPECTIVE: When you stand in the middle of a road that
pinches together at the horizon, you are experiencing
perspective. Perspective is also used to relate nearness of objects to one another. Usually closer objects are larger than farther objects, for example. You can control this with your camera through focal length Wide-angle lenses increase perspective and telephoto lenses flatten perspective. Telephoto lenses are used in Hollywood films to make it appear as if the star is closer to: the vehicle running him down / exploding fuel drums / mob chasing him etc.