Glossary

ambient light is the light on the scene (natural or artificial) without any being added by the photographer.

aperture is the variable opening in the lens that admits light into the camera. It is expressed as an f-stop (f/5.6, f/16, f/22, . . .) number. The lower the f-stop number, the larger the aperture. See also depth-of-field and f-stop.

aperture priority mode is a setting available on more expensive cameras that lets the photographer set the aperture and the camera automatically selects the shutter speed. Use this when you want to control the depth-of-field.

archival  refers to the permanence of a photograph—an issue for all collectors of fine prints. Materials and methods of processing have been developed to maximize the archival quality of the medium. Acid-free paper is more likely to last longer than paper which is not, and is often labeled "archival." But the term is tossed around so freely that one should be cautious about assuming the image will not deteriorate over time.

ASA (or ISO) is a system for rating the sensitivity to light of film or the photocells in a digital camera. Most digital cameras today use the ISO rating designation, which is identical. An ISO (or ASA) rating of 100 means the film or camera’s sensitivity is lower than one set at an ASA/ISO of 800. But a low ASA/ISO usually results in a smoother appearance with less “grain.” See also ISO.

backlight is the light that project towards the camera from behind the principal subject. It may be natural or set up by the photographer to create a backlit subject.

bracketing means making additional exposures that are often both 1 or 2 f-stops over and 1 or 2 f-stops under the indicated exposure.

color temperature Ordinary light includes a distribution of different colors in a more-or-less continuous spectrum. Light sources are measured by their color temperature in "degrees Kelvin." Some color film is balanced for artificial light and others for natural light. In many digital cameras one may set the white balance to compensate for the color of the light. See also white balance.

contrast in photography is the difference between the brilliant (or light) and the dense (dark) areas of an image. A high contrast image is one with both very bright white/highlights and very deep shadows. A low contrast image (such as you might get on a foggy morning) would have no highlights and perhaps no areas entirely black.

convergence means that two (or more) lines or edges appear to come together in the distance although they are parallel in reality and when viewed up close. The best examples are railroad tracks and a skyscraper.

daguerreotype was the first successful photographic process. Its principal inventor was Louis Daguerre, in 1839, although several others contributed significant ideas, foremost among whom was Joseph Niépce who had produced crude images in the 1820s on pewter coated with pale colored bitumen. A daguerreotype is often a sharp image, but as there is no negative, additional prints could not be made from it.

depth-of-field is an area extending in front of and behind the point of sharpest focus in which the subject is acceptably sharp. For a landscape you generally want a large (or deep) depth of field (everything in focus), but for a portrait you may prefer a short depth-of-field (all but the subject's face is slightly out of focus). To maximize the depth of field set the camera at its smallest aperture (f/22 or greater) and focus about one-third of the way up from the bottom of your picture.

dodging & burning are operations carried out in the darkroom to, respectively, lighten and darken selected parts of the print by briefly shielding (or exposing to additional light) parts of the image during exposure. Photo editing programs such as Photoshop employ similar tools.

EXIF or EXchangeable Image File format. Is metadata, or information attached to a file by a digital camera. It is widely used to store information about the camera's settings (such as shutter speed, aperture, ISO, etc.) and when the image was captured.

exposure is the total light reaching the film. It is determined by the luminance (brightness) of the subject, the aperture setting, the shutter speed and the film speed (the ASA/ISO rating). Photographers often say, "increase the exposure by one f-stop," or "stop down by two f-stops." One can increase the exposure by using a larger aperture or by using a slower shutter speed.

film speed is a measure of a film's sensitivity to light. Faster films tend to have more grain and less resolving power.

f-stop is a measure of the aperture opening. An f-stop of f/8 admits twice the amount of light as an f-stop of f/11. The f-stop numbering system is initially confusing because the smaller the number, the larger the aperture. f-stops are sequenced in this manner: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, etc. Increasing the f-stop by one stop (say from f /8 to f/11) halves the light reaching the film; decreasing the aperture by one f-stop (say from f/16 to f/11) doubles the amount of light.

fill flash is light provided by a camera-mounted flash to put light into shadow areas and thus reduce lighting contrast.

focal length is the distance from the lens to the surface of the film or CCD sensor (the plane of focus) where the light rays come together. The term is used to refer to the size of a lens; thus, a telephoto lens is of greater focal length than a wide angle lens.

gray card is a gray piece of cardboard used to provide a standard measure of the amount of light reflected by a surface. The gray represents an average tonal value, defined as 18% of the light falling on it. In the Zone System, that is a middle tone, termed Zone V. See also Zone System.

gray scale is a printed strip of tonal values, from pure black to pure white, usually divided into 10 zones. Each zone requires twice or half the exposure as the zones on either side. See also Zone System.

high key images are characterized by a predominance of lighter tones. The subjects are normally white or pale in tone, and the photographer uses flat overall lighting to avoid shadows.

incident light is the light falling on a subject before it has been reflected by that subject. Some light meters measure incident light and others measure reflected light. A camera's built-in metering system measures reflected light only.

ISO is a system for rating the sensitivity to light of film. It has been adopted by digital camera makers to indicate the relative sensitivity of the recording medium. Most digital cameras today use the ISO designation instead of the ADA designation, but the meaning of two terms is identical for our purposes. An ISO (or ASA) rating of 100 means the film or camera's sensitivity setting is less than one set at 800. Not all cameras permit adjustment of the ISO, but if they do, one is well-advised to keep the setting rather low, as the color saturation and contrast are reduced with high settings.

matrix metering is an reflected light metering system built into many digital camera. It interprets a series of readings from different points around the frame to arrive at a suggested exposure.

overexposure means there was too much light striking the photosensitive material. Underexposure means there was too little light for a good image.

shutter is a mechanical system in a camera for controlling the amount of time of the exposure.

shutter priority mode is a setting available on more expensive cameras that lets the photographer set the shutter and the camera automatically selects the aperture. Use this when you want to “stop” the action, or when you want to show the motion blur of a sports scene or a waterfall, for example.

shutter release is the button that one presses to take the picture.

shutter speed is time the shutter is open during exposure. A typical combination for many landscape photographers might be a shutter speed of 1/60 of a second and an f-stop of f/16, assuming one has a reasonably bright day and an ISO of 100-200. The standard sequence of shutter speeds for both digital and film cameras is 1 (second), 2 (one-half second), 4 (one-fourth second), 8, 15, 30, 60, 125, 250, 1000, ..., where 60 represents 1/60 of a second, 125 represents 1/125 second, etc.

soft focus is a blurred or slightly out-of-focus image, often deliberately done to create a special mood.

reflectance is the amount of light rebounding off a subject. It is what the camera's built-in lightmeter reads.

white balance is simply an adjustment, made in the camera or in your photo editing software, to get the color to look right. The color of light in the shadows, under a fluorescent fixture, and in the shade, for example, does not always come out right. But it can often be adjusted without introducing any false color by adjusting the white balance. Consult your camera's manual for how to do this.

Zone system is a technique developed by Ansel Adams and Minor White to interpret meter readings of light intensity and translate those readings into a means of controlling exposure and development of film. It requires an understanding of the gray scale, which divides measurable light into 10 zones, each zone up from pure black representing twice the amount of light. See also gray scale.