Photography 1 ch 2

depth of field,

Aperture and Depth of field The smaller the aperture size, the more of a scene that will be sharp from near to far. As the aperture is stopped down and gets smaller, more of the background and foreground in a given scene becomes sharp. The area of acceptable sharpness in a picture is known as the ______ ____ ________. The two larger photographs shown on these pages were taken under identical conditions but with different aperture settings. In the photograph above, the diaphragm was opened to its widest aperture, f/2, and the lens was focused on the boy (b) about seven feet away (see side view Of photographer Duane Michals and his subjects, above right). The resulting photograph shows a shallow depth of field; only the middle boy (b) is sharp, while both the boy in front (a) and the man behind (c) appear out of focus. Using a small aperture, f/ 16, gives a different picture (opposite page). The lens is still focused on the middle boy, but the depth of field has increased enough to yield sharp images of the other figures as well. Some types of cameras let you see the extent of the depth of field. With a view camera, you look directly through the lens. As the lens is stopped down, the increasing sharpness is visible on the ground-glass viewing screen. A single-lens reflex camera also allows you to look directly through the lens. But most models, regardless of which aperture is selected, will automatically show the scene through the widest aperture. They are designed this way because looking through the lens at its widest aperture gives you the brightest possible view for framing and focusing. Depth of field is the area from near to far in a scene that is acceptably sharp in a photograph. As the aperture changes, the depth of field changes. If your lens has a depth-of-field scale (many do not), you can use it to estimate the extent of the depth of field. On this lens, the bottom row shows the aperture (f-stop) to which the lens is set. The top ring shows the distance on which the lens is focused. The paired numbers on the middle ring correspond to f-stops and show the nearest and farthest distances the depth of field covers when the lens is set at various f-stops. Here, the lens is set to its widest aperture, f/2, and focused on the middle boy (see side view of scene above), who is at a distance of 7 ft. The depth of field extends from more than 6 ft to less than 8 ft; only objects within that distance will be acceptably sharp. If depth of field is shallow, as it is here, a lens can be sharply focused on one point and still not produce a picture that is sharp enough overall. When the lens is stopped down to its smallest aperture, heref/16, the depth of field increases. Almost the entire scene—everything between about 5 ft and 13 ft—is now sharp at the same focusing distance of 7 ft. NOTE: The bigger the f-stop number, the smaller the lens opening (you can see this illustrated on page 25); f/ 16 is a smaller aperture than f/2. Looking through the widest aperture also means you see the scene with the least possible depth of field. Some cameras provide a depthof-field preview button that stops down the lens so that the viewfinder image shows the depth of field at the aperture you have selected. However, stopping down the lens reduces the brightness of the viewfinder image. In dim light or at a very small aperture, that image may become too dark to be seen clearly, but single-lens reflex film cameras and view cameras do give you a way to check depth of field visually at all apertures. With a digital camera you can make (and later delete) a test shot to evaluate depth of field from the monitor display. Other camera designs show the scene differently. Rangefinder and some compact camera designs have a window in which you frame your shot. Through this viewfinder, objects at all distances appear equally sharp. Some lenses have a depth-of-field scale from which you can estimate the depth Of field. This scale is printed on the lens as paired numbers that bracket the distances of the nearest and farthest points of the depth of field. As the lens is focused and the f-stop set, the scale shows approximately what part of the picture will be in focus. (See the lenses at left.) The farthest distance marked on the lens appears as the symbol 00. When this infinity mark appears within the depth of field shown on the scale, all objects beyond the closest distance in focus will be sharp. Look up the depth of field in a table if your lens has no scale. Published tables give depth of field for every focal length, aperture, and distance. Check a library or online; see page 58 for more.

combination, Equivalent, opposite, reciprocal,

Using shutter and aperture together Both shutter speed and aperture affect the amount of light entering the camera. To get a correctly exposed picture (one that is neither too light nor too dark), you need a ______ of shutter speed and aperture that lets in the right amount of light for a particular scene and particular ISO speed. _____ exposures. Once you know a combination of shutter speed and aperture that will let in the right amount of light, you can change one setting as long as you change the other in the _____ way. When using full stops, each aperture setting lets in twice as much light as the next smaller opening (larger-numbered setting). Each shutter speed lets in twice as much light as the next faster speed. (See photographs at right.) You can use a larger aperture if you need a faster shutter speed, or you can use a smaller aperture if you want a slower shutter speed. The same amount of light is let in by the combination of f/16 aperture at a 1/8-second shutter speed, as by fill at 1/15 second, and so on. This back-and-forth balance is called a ____ relationship. Shutter speed and aperture also affect sharpness, but act differently. Shutter speed affects the sharpness of moving objects; aperture affects depth of field, sharpness from near to far. Their different effects are shown in the three photographs at right. In each, the lens was focused on the same point, and shutter speed and aperture settings were balanced to admit the same total amount of light into the camera. But the equivalent exposures resulted in very different photographs. In the first picture, a small aperture produced considerable depth of field that rendered background details sharply. But the shutter speed needed to compensate for this tiny aperture had to be so slow that the rapidly moving flock of pigeons appears only as indistinct ghosts. As the aperture was set wider and the shutter speed faster in the middle photo, the background is less sharp, but the pigeons are visible, though still blurred. At far right, a still larger aperture and faster shutter speed sacrificed almost all background detail, but the birds are now very clear, with only a few wing tips still blurred.

focal-plane

A ___-____ shutter is built into the camera body and is located directly in front of the sensor or film; it consists of two overlapping curtains. When the shutter is released at slow shutter speeds, the first (opening) curtain moves across the frame, revealing a window through which the sensor or film is exposed. The shutter waits for the correct amount of time, then it closes the second (following) curtain to stop the exposure. At higher shutter speeds, the following curtain begins to close before the opening curtain has completed its travel. The film or sensor is exposed through what appears to be a moving slit. As the shutter speed increases, this slit narrows. The series to the right shows the shutter travel at fast shutter speeds. The narrow slit exposes only part of the frame at any one time, but every part of the sensor or film receives light for the same amount of time. Above, see the effect of the entire exposure, with all sections of the sensor or film having received the proper amount of light. The shutter shown here moves from side to side. Some cameras have another type of focal-plane shutter (called a guillotine) that moves from top to bottom. Some digital single-lens reflex cameras use an interline transfer CCD sensor (see text at left). They also have a focal-plane shutter but do not use it to control the length of exposure. Advantages/Disadvantages. Interchangeable lenses for a camera with a focal-plane shutter can be less expensive than those for cameras requiring leaf shutters, because a shutter does not have to be built into each lens. And focal-plane shutters can reach higher speeds than leaf shutters—as high as 1/8000 sec. Generally, however, you can't use electronic flash when both shutter curtains are moving at the same time. The highest shutter speed at which the opening curtain has completed its travel before the following curtain begins to move—called the sync speed—may be as slow as 1/60 second. At any faster shutter speed than a camera's sync speed, a flash will illuminate only the slice of the frame revealed by the slit at the moment the flash is triggered. Because you must use a relatively slow shutter speed with flash, bright existing (or ambient) light may register on the film or sensor as well as light from the flash. This can leave a "ghost" or second image in the picture.

smaller, larger, amount,

F-STOPS: controlling the size of the lens aperture Lenses come with a limited range of apertures (f-stops) usually marked in full stop increments. Each full stop lets in half the amount of light as the one before it and double that of the one after it. (Note that the ______ the f-number, the _____ the lens opening.) Apertures are continuously variable; on many cameras they can be set anywhere in between full stops. But your lens or display may only indicate one-half or one-third stop increments. This chart shows a range of full and fractional aperture openings. Not all cameras number the fractional apertures exactly as shown. If your camera allows you to choose among different ways to set apertures, using full stops will be less confusing while you learn photography The size of the lens opening—the aperture or f-stop—controls the ______ of light that passes through the lens. The lens shown here has apertures from f/ 2.8 to f/22. Each setting is one stop from the next; that is, each lets in twice as much light as the next smaller opening, half as much light as the next larger opening. The higher the f-stop number, the smaller the lens opening and the less light that is let in. On this lens, f/2.8 is the largest opening and lets in the most light. As the numbers get bigger (4, 5.6, 8), the aperture size gets smaller and the amount of light admitted decreases. NOTE: Some lens barrels do not display the apertures as shown above. Rather than twisting a ring on the lens to set the aperture, you dial in the setting on the camera body. Regardless of how you change the aperture, though, you are still changing the size of the lens opening and thus the intensity of light that strikes your film or sensor. f/2.8 Twice as much light as f/4 f/4 Half as much light as f/2.8 Twice as much light as f/5.6 f/5.6 Half as much light as f/4 Twice as much light as f/8 f/8 Half as much light as f/5.6 Twice as much light as f/ 11 f/ll Half as much light as f/8 Twice as much light as f/ 16 f/16 Half as much light as f/ll Twice as much light as f/22 f/22 Half as much light as f/16 Greatest Depth of Field WHERE APERTURE SETTINGS ARE DISPLAYED ON VARIOUS CAMERAS 1) In the camera's viewfinder 2) In the data-panel readout 3) On the lens barrel

leaf, lens

HOW Shutters WORK A _____, or between-the-lens, shutter is generally located inside the _____ itself. All view cameras, many medium-format cameras, and most compact cameras use leaf shutters. The leaf shutter consists of a number of small overlapping metal blades. As shown at right, when the shutter is released, the blades open up for an amount of time determined by the selected shutter speed, then shut again. The total amount of light admitted during this cycle produces the fully exposed photograph (see top of the page). Many compact digital cameras use a particular kind of CCD sensor (called interline transfer) that controls the length of exposure electronically. Most of these have a leaf shutter that is normally open, but closes momentarily before exposure to allow the sensor to initialize. Advantages/ Disadvantages. A leaf shutter is quieter than a focal-plane shutter and can be used with flash at any shutter speed. But because the leaf shutter has to open, stop, and then reverse direction to close again, most have top speeds no higher than 1/500 second. If your interchangeable-lens camera uses leaf shutters, the shutter is probably built into the lens. The cost of a shutter then adds to the price of each lens. Also, actual shutter speeds for the shutter in one lens might be a little slower or faster than those for the shutter in another. Generally, the difference is small, but it could be enough to make a noticeable difference in exposure when changing from one lens to another. Because a leaf shutter only has to open until it reaches the outer edge of the aperture, many cameras can set a higher shutter speed for small apertures than for large ones. Leaf shutters are so quiet that many compact digital cameras are programmed to emit an electronic shutter-like sound when the button is pressed so the user can tell when an exposure has been made.

aperture, diaphragm, f-stop,

The Aperture The aperture and light The _____ (the size of the lens opening) controls the brightness of the light that reaches the sensor or film. The aperture works like the pupil of an eye, enlarging or contracting to admit more light or less. In a camera lens, the _______—a ring of thin, overlapping metal leaves located inside the lens—is the mechanism that controls the size of the aperture. Its movable leaves can be opened wide to let in more light or closed down to let in less (see opposite). The size of an aperture is indicated by its f-number or ________. On early cameras the aperture was adjusted by individual metal "stop" plates that had holes of different diameters. The term stop is still used to refer to the aperture size, and a lens is said to be "stopped down" when the size of the aperture is decreased. Part of the standardized, full-stop series of numbers on the f-stop scale is shown in the box, right. The smaller numbers correspond to the larger apertures, and admit the most light. Each larger-numbered full f-stop (shown in boldface) admits half the light of the previous one. A lens that is set at f/4 admits half as much light as one set at f/2.8 and only a quarter as much as one set at f/2. (Notice that f-stops have the same half or double relationship that full-stop shutter-speed settings do.) The full-stop numbers continue in both directions. Wider apertures, for example f/ I or f/O.7, are possible but such lenses are too expensive for general use. Smaller ones— f/ 32, f/45, f/64, f/90—are seen only on specialized lenses. The change in light over the full range of f-stops is large; a lens whose aperture is stopped down to f/64 admits less than 1/4000 of the light that comes through a lens set at f/ l. Few lenses provide a range of apertures greater than eight stops. A general purpose lens for a single-lens reflex camera, for example, might run from f/ 1.4 to f/ 16. A camera lens designed for a large view camera might stop down to f/64 but open up only to f/5.6. NOTE: The widest possible aperture on your lens may not be a standard full stop. A lens's f-stops may begin with a setting such as f/ 1.2, f/3.5, or f/7.7, then proceed from the next full stop in the standard sequence. Lenses are often described as fast or slow. These terms refer to the width of the maximum aperture for the lens. A lens that opens to f/ 1.4 opens wider and is said to be faster than one that opens only to f/ 2. Faster lenses allow you to shoot more easily in low light or at higher shutter speeds. They also are more expensive than slower lenses. A fast lens, one that opens to a wide aperture, is useful in dim light, such as indoors. A wide aperture lets you set a shutter speed fast enough so that you don't have to use a tripod to keep the camera steady. It is also useful when photographing action by letting you shoot at a fast enough shutter speed to show moving subjects sharply.

exposure, bulb, stop

The Shutter The Shutter and Light Two controls adjust the amount of light that reaches the sensor or film: the shutter, described here, and the aperture (pages 24—25). The combination of an aperture and a shutter speed is an _______, which must be a correct one so your picture is neither too light nor too dark. Adjusting the length of time the shutter remains open controls the amount of light that reaches the light-sensitive surface. Doubling the amount of time it is open gives one stop more exposure—twice the amount of light. Halving the amount of time gives one stop less exposure—half the amount of light. Each full-stop shutter setting is half (or double) the time of the next one and is marked as the denominator (bottom part) of the fraction of a second that the shutter remains open: 1 (1/1 or one second), 2 (1/2 second), 4 (1/4 second), and so on through 8, 15, 30, 60, 125, 250, 500, 1000 or higher. Some cameras have shutters that reach 1/8000 of a second. B (_____ setting) keeps the shutter open as long as the release button is held down. T (______ setting) opens the shutter with one press of the release, and closes it with another. Electronically controlled shutters can operate at any speed, for example, 1/38 second. These "stepless" speeds are set by the camera in automatic exposure operation; some cameras allow you to dial them in yourself—others don't. Some digital cameras use a shutter for exposure. Others use them only to block light when the sensor needs darkness; they control exposure by turning the sensor on and off for a precisely timed duration (see How Shutters Work, opposite). NOTE: The term "______" in photography refers to a change in illumination, whether the shutter speed or the aperture is changed to achieve it. To give one stop more exposure means to double the amount of light reaching the light-sensitive surface, either by doubling the exposure time or by doubling the size of the aperture (see page 25). To give one stop less exposure means to cut the light reaching the sensor or film in half by halving the exposure time or by halving the size of the aperture. WHERE SHUTTER SPEED SETTINGS ARE DISPLAYED ON VARIOUS CAMERAS 1) In the camera's viewfinder 2) On the shutter-speed dial 3) In the data-panel readout For the above examples, each camera is set to 1/500 sec. Notice that the camera displays only the bottom number of the fraction.

viewfinder, shutter-speed, aperture, Interchangeable

The _______ shows you the entire scene that will be recorded and indicates which part of the scene is focused most sharply. The viewfinder usually displays exposure information—here the shutter speed (1/250) and aperture (f/ 16). The ___-____ selector controls the length of time that the shutter remains open. A shorter time decreases the likelihood that a moving object will appear blurred. The _____ selector adjusts the size of the lens opening—created by the blades of the diaphragm. The smaller the aperture opening, the greater the depth of field (the part of the scene from near to far that will be sharp). ________ lenses let you select the lens focal length, which controls the size of objects in the picture and the extent of the scene that will be recorded on the film or captured digitally.

shutter speed, aperture

The basic camera controls The basic controls on all cameras are similar, helping you to perform the same actions every time you take a picture. You'll need to see the scene you are photographing, decide how much of it you want to include, focus it sharply—where you want it to be sharp—and use the shutter speed (the length of time the shutter remains open) and aperture (the size of the lens opening) to expose the sensor or film to the correct amount of light. One of the most popular camera types is shown here—the single-lens reflex. Other basic camera designs are described later in this chapter. As the camera's settings change, the picture changes also. What will a scene look like at a faster shutter speed or a slower one? How do you make sure the background will be sharp—or out of focus—if you want it that way? Once you understand how the basic camera controls operate and what your choices are, you will be better able to get the results you want, rather than simply pressing the button and hoping for the best. Mode dial: to set manual or one of several choices of automatic operation Data panel: displays ISO, shutter speed and aperture settings, number of exposures remaining, and other information Memory card: (inside the camera) stores the image. LCD monitor: displays stored images and menus for camera settings. Digital Camera: An array of controls on these single-lens reflex digital cameras let you make settings manually or automatically, and view (and delete if you wish) the photograph you have just made or any others on its memory card. Control Dial: for manually slecting shutter speed and/or aperture Data panel Focusing Ring: for manually focusing the lens MANUAL FILM CAMERA Manually adjusted controls on this 35mm single-lens reflex camera let you set the ____ ____ (the length of time the shutter remains open), select the lens ____ (the size of the lens opening), focus on a particular part of the scene, and change from one lens to another. AUTOMATIC FILM CAMERA On automatic cameras, control keys often replace adjustable knobs or rings. This model automatically adjusts the focus, shutter speed, and aperture. You can override the automatic features if you want to adjust the camera's settings yourself. Built for professionals, it has a complete system of lenses and accessories.