Aperture: How much light your camera lets into the camera. Also known as F-Stop. A higher number lets in LESS light, but gives GREATER depth of field. A smaller number lets in more light, but gives LESS depth of field. The widest aperture currently available for photography is f/1.2, resulting in an extremely shallow depth of field.
Aperture Priority Mode: This camera setting is used to lock in a constant aperture, while shutter speed and ISO are varied to achieve the correct exposure. This mode is routinely used when one wants to select a particulat aperture setting to control depth of field, as in landscape photography.
Astrophotography: Taking photographs of the night sky. The moon is the brightest object you can photograph. Everything else is pretty faint, so more light is always better. The bet results are obtained using a platform that will compensate for the earth’s rotation, so you can use very long exposures without blurring. If possible, get a lens (or telescope) with the largest aperture possible. Importantly, resolution is almost never limited by the camera you are using, but by the lens and tracking equipment.
Autofocus: A machanism in your camera that detects the contrast of an image, focusing the lens so this contrast is maximaized. Modern cameras are extremely quick and accurate at focusing, except in very dim conditions.
Autofocus Assist Lamp: Digital cameras use "contrast detection" when they focus on something. When light levels are low, the camera can't focus on the object. Without proper focus, some cameras won't take the picture, while others focus on infinity. Autofocus lamps eliminate this problem by shining a bright light on the subject so the autofocus mechanism can "see" the subject properly. With modern cameras, this is really only a problem in dimly-lit indoor conditions.
Bokeh: A term referring to the out-of-focus areas of a photograph. Bokeh is especially significant in large-aperture lenses. Some lenses produce more subjectively pleasing bokeh than others. This may be especially important in portrait photography, where a pleasantly-blurred, non-distracting background is desired. Lenses with few elements in their aperture rings typically leave polygonal bokeh, while those with more elements (which more closely approximate a circle) leave more circular ones. Mirror (reflector) lenses typically leave unpleasant bokeh with false detail.
Bracketing: When you take a series of exposures ranging from underexposed to over-exposed. When you get back home, you can pick the one that you think is best. This can also be done with varying flash levels (flash exposure bracketing).
Chromatic Aberration: Occurs because light of different wavelength (red vs. violet) passes through the same piece of glass with a slightly different refractive index. This results in the purple “ghosting” seen in some photos. Chromatic aberration is more of a problem at long focal lengths. Most high-quality modern telephoto lenses are made with glass that minimize chromatic aberration. Nikon calls this ED (extra-low dispersion) glass, and can be identified by the gold band around the lens barrel.
Continuous shooting (burst) mode: The ability of a camera to take multiple frames sequentially, measured in frames per second. Most compact digital cameras can take 1 to 3 frames per second up to 10 frames. Higher end SLR cameras can take up to 7 frames per second for dozens of frames, even in RAW file format mode.
Depth of Field: This is the measure of whether near and far objects are both in focus. A narrow depth of field will only have an object at a specific distance in focus, while a wide depth of field will have almost all distances in focus. You can determine the depth of field through the aperture of your camera. A wider aperture (for example f/2.8) will have a narrower depth of field than a narrower aperture (for example f/22). Digital cameras with small sensors tend to have a wide depth of field even at wide apertures.
Depth of field preview: When you look through an SLR’s viewfinder, you are looking through at its widest aperture setting, which results in the narrowest depth of field, but also the brightest image. The depth of field preview button allows you to see what the depth of field will actually look like at the selected aperture.
Digital Camera: Instead us using film to capture light, a digital camera uses a sensor made of silicon. The sensor has discrete areas, called pixels, that capture this light. This is where the term “Megapixels” comes from. Each “megapixel” represents one million discrete areas with which a camera’s sensor collects light. When a photon of light strikes a camera’s sensor, this photon is transformed into an electrical current, which is recorded by the camera. The more photons that hit a pixel, the brighter that pixel appears.
Digital Zoom: A dumb idea for cheap (crappy) cameras. The "zoom" simply crops your picture like you would in Photoshop to make the final picture look larger. The problem is that you lose resolution in the process. Your pictures will look more pixelated, and unless you want a small print, you will not be happy. Optical zooms do NOT lose resolution, and thus are far superior.
EXIF Data: Information that a camera records about the parameters of a photograph, such as shutter speed and aperture.
Extension Tube: A tube used to increase magnification which is placed between the camera and the lens. The tube is hollow, and has no glass in it. Extension tubes can be used for both long distance and macro photography.
Filter: Something placed in front of a camera's lens to alter the image in some way.
Fisheye Lens: An ultra-wide lens that has an extremely wide angle of view (as much as 180 degrees). To achieve this ultra-wide view, these lenses sacrifice rectilinear images for a distorted convex image.
Flash synchronization speed. The maximum speed that a camera can shoot while the flash is firing. Some cameras are as slow as 1/100 of a second, while others are faster than 1/500 of a second.
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Focal Length: The measure of a lens' ability to magnify an object. A higher number will make an object appear larger (a telephoto lens, like looking through a telescope).
Histogram: A graphic representation of the brightness values on a photograph.
IS and VR: Canon calls it "Image Stabilization: and Nikon calls it "Vibration Reduction" Both do the same thing. These lenses use gyroscopes to track camera movement, and have motors attached to a lens element to counteract camera shake. This can result in dramatically sharper hand-held photos. Nikon claims that you can shoot 3 F-stops faster. This is true, by the way. However, these systems can only counteract camera motion, not subject motion. So if you want to shoot at a sporting event with lots of subject motion, there's still no substitute for a fast lens.
ISO: The film's (or sensor's) sensitivity to light. A higher number is more sensitive to light. For example, ISO 800 is twice as sensitive as ISO 400. This means that if you switch from ISO 400 to 800, you can cut exposure time in half with the same results, or can reduce the aperture with the same results. Importantly, increasing ISO results in more film grain in film cameras, and more noise in digital cameras. However, a high ISO image with noise almost always looks better than a low ISO image with motion blur. Interestingly, most modern digital cameras offer far higher ISO sensitivity than film cameras ever did. While film maxed out at ISO 400 or ISO 800 for some specialty films, some modern digital cameras can give usable results at ISO 6,400 (a whole eight times more sensitive!!!). With such a high ISO possible, digital photographers don't have to carry lenses that are as "fast" as they used to. Another bonus is that you can change ISO on digital cameras at a whim, where with film cameras, you're stuck with that ISO for the whole roll of film.
Lens hood: A device that attaches to a lens to prevent glare and lens flare. Some are conical, but others have a more complex cut to keep the hood from blocking the field of view. Hoods are more common in telephoto lenses. Hoods can usually be mounted backwards on the lens for storage purposes. Some people find it easier to simple block the sun with their hand than use a lens hood. Lately, the use of large hoods has become fashionable, mostly because it makes a lens look larger (and more expensive) than it actually is.
Lens Speed: The maximum aperture of a lens. A lens with a large maximum aperture (low F-stop) will let in more light, allowing a faster shutter speed for a given light condition. An F-3.2 lens is "faster" than an F-4.5 lens. "Faster" lenses tend to be larger and more expensive. The most expensive zoom lenses have a maximum aprture of f/2.8. Prime (fixed focal length) lenses can have maximum apertures as low as f/1.2.
Macro Lens: Sometimes called Micro lenses. These are used for close-up photography, and are able to focus at extremely close distances. Frequently, these lenses project an image on the camera's sensor that is larger than the object itself. Macro lenses are useful for photographing small objects such as insects.
Megapixel: One megapixel equals one million pixels in a camera's image. For example, a 6 megapixel camera has 6 million pixels in its final image. You can determine the number of megapixels in an image by multiplying the width (in pixels) by height (in pixels). So a 3000 X 2000 pixel image has 6,000,000 pixels, or 6 megapixels.
Mirror Lens: These lenses use a mirror in their rear surface to reflect the image to another mirror at the front surface, which then finally reflects the image to the camera's sensor. This effectively folds the focal length in half, enabling telephoto mirror lenses to be much smaller, lighter, and cheaper. However, these lenses do not have as much optical quality or contrast as traditional refractor lenses.
Mirror Lockup: This is an option on most SLR cameras that puts the mirror in the UP position well before the shutter fires. Why, you ask? When the mirror flips up, it induces small vibrations which lead to camera shake which causes blurring. This effect is worst at shutter speeds between 1 and 1/30 sec., especially at long focal lengths. Flipping the mirror up in advance allows the vibrations to die down before the exposure is taken. In reality, using mirror lockup is only useful when you are shooting at long focal lengths and you need the sharpest detail possible. There are usually many other factors that contribute far more to camera shake than mirror movement. This option is also useful for cleaning the camera’s sensor, because reaching the sensor is impossible with the mirror in the way.
Moire patterns: An undesired artifact in digital photographs. They occur when there's an area of repetitive detail that exceeds the resolution of the camera (in technical terms, undersampling a fine, regular pattern).
Neutral Density (ND) Filter: This type of filter reduces the intensity of all wavelengths equally. It is like putting a pair of gray sunglasses over your lens. It is useful for situations where you want to take a longer exposure (e.g. waterfall) in high light conditions. It is also useful when you want to open up the aperture in high light conditions to minimize depth of field, as in a portrait. For landscape photography, you can use a graduated ND filter to darken the sky, thus lightening the foreground and bringing out more detail.
Night Photography: Photographs taken between twilight and dawn. These photographs almost always require long exposures, necessitating a tripods or other method of camera stabilization. Exposure times can range from seconds to minutes. Night photogrpahers prefer wide-aperture lenses to minimize the exposure time.
Noise: Noise is apparent by the presence of color speckles where there should be none. How can we eliminate this? One way is to use a camera with a large sensor, such as a DSLR. Small point and shoots tend to have much smaller sensors (and a much smaller physical size), and thus more noise. You also get less noise with a lower ISO sensitivity. Longer exposures also tend to introduce more noise. Also, you can use noise-reducing algorithms in Photoshop, or your camera may have its own noise-reducing mode.
Optical and Digital Image Stabilization: One is real, the other is FAKE!!! Optical image stabilization is far superior. These systems use motion sensors to detect camera movement, and also little motors to move glass elements in the lens to counteract camera movement. The fake kind simply raises the ISO (which you can do anyways) so you can use a higher shutter speed. And a higher ISO comes with more noise. So it's basically worthless.
Pancake Lens: An extremely short prime, manual focus lens based on the Zeiss Tessarr design developed at the turn of the 19th century. It's main advantages are that it's extremely sharp and compact, but relatively slow by modern standards (f/2.8). The lens is popular among people who need the most compact SLR's possible, like street photographers.
Polarizing filter: This filter lets through only one polarization of light. Light from the sun is emitted in every polarization, but when this light is reflected off of an object, such as a droplet of water in the atmosphere or a lake, only one polarization remains. Thus, polarizing filters are useful in eliminating these reflections. One can see through the surface of water or darken the sky. Importantly, in the sky, polarizing filters are maximally effective 90 degrees from the sun. This can be a problem with wide-angle lenses, since one part of the sky will look darker than the other.
Prime Lens: A fixed focal length lens which cannot zoom. The advantages to a prime lens are that it usually has a larger aperture (as large as f/1.2), has less distortion, and is much lighter in weight than most zoom lenses. Proponents of prime lenses often advocate "zooming on your feet." That is, the same effect of a zoom lens can almost always be achieved by moving closer to she subject.
Red Eye: When a picture of a person is taken with flash, the light from the flash will pass through the subject’s cornea tot eh back of their eye (the retina). The light then bounces back from there, back through the cornea, to the camera. The problem is that the retina is rich in blood, and this red color is transmitted back to the camera. The effect is worse in low-light conditions when peoples’ pupils are more dilated (and you’re more likely to use a flash). Interestingly, some species, such as dogs and cats, have a reflective coating on their retinas (the tapedium) which intensifies this effect (and also allows them to see better at night). Many modern cameras have red-eye reduction features. The series of low-power flashes that precede the main exposure in some cameras is designed to constrict the subject’s pupils, lessening red-eye.
Reverse Mount: An adapter that allows you to mount your lens backwards so you can focus on very lose objects (for macro photography). To see how it works, just take your lens, flip it around, and hold it against the camera. This technique can yield great results. Adapters can be had for about $10.00. Unfortunately, you will likely lose metering and autofocus, but these are generally not that important for macro photography anyways. Be sure to use a lens with a manual aperture ring, or you will be stuck having to control the aperture with the tiny little stick at the front (formerly back) of the lens.
Sensor size: Most digital camera sensors are far smaller than the “full-frame” sensors of a 35mm equivalent digital camera. The problem of building a sensor the size of a 35 mm camera is that producing a flawless piece of silicon that size is extremely difficult and expensive. Having such a large sensor reduces noise, and produces excellent images.
Most digital cameras do not use “full frame sensors.” For example, the Nikon D40 uses a smaller sensor. When used with a normal focal length lens, this smaller sensor results in a focal length 1.5X as large. Canon’s sensor is only 15X22 mm in size. Nikon’s size is 16 X 24 mm. Nature photographers love this, since it offers more magnification, but macro photographers don’t, since it means that their wide lenses don’t go nearly as wide as with a traditional 35 mm frame camera.
Shutter speed: The length of time (in fractions of a second) that the film or sensor is exposed to light. A longer speed lets in more light, but the image may be degraded by camera or subject motion. A faster speed is better at "freezing" the motion, but this may not be possible in low-light conditions. In general, shutter speeds can vary from 30 seconds or more to 1/8000 of a second. Quite a huge range.
Shutter Priority Mode: This setting on a camera allows you to set a single shutter speed, while the camera varies aperture and ISO to achieve a good exposure. This mode is routinely used to lock in a long exposure to achieve motion blur in the exposure.
Silent Wave Motor: What Nikon calls the in-lens motor that drives the auto focus of their new lenses, introduced in 1996. Instead of using a motor inside the body to drive the autofocus mechanism, is located within the lens itself. The SWM uses ultrasonic vibrations to directly drive the focus elements within the lens. This enables nearly silent, very fast, and accurate autofocus operation, since no gears are involved. However, AF-S lenses generally must be focused manually on older Nikon bodies since they are not backwards compatible.
SLR: Stands for "Single Lens Reflex" This is a type of camera in which the viewfinder is a direct representation of the image about to be captured. You see exactly what you get. The light enters through the lens and then is diverted with a mirror into the eyepiece. When the exposure is taken, the mirror flips out of the way, and the light hits the film (or sensor). When the exposure is finished, the mirror flips back down again, and the photographer can again view the subject through the lens.
Soft Focus: Occurs when an image is blurred due to spherical aberration. One can buy a soft focus lens that deliberately introduces spherical aberration into the image, which will give the appearance of a blurred image while retaining sharp edges. This yields a soft, dream-like image that hides blemishes. Note that this effect is NOT the same as an out of focus image, so defocusing your lens will not work. Sometimes the effect is approximated by using a diffusion filter. The effect can also be simulated easily in Photoshop.
Stock Photography: Photographs that are bought by a company and stored in a database. These photographs are licensed to publishers, advertising agencies, and other companies for their use.
Teleconverter: An auxiliary lens placed between the camera body and the lens. The purpose of a teleconverter is to magnify the image from the lens, yielding a longer focal length. This will make the image appear larger than it normally would. However, this magnification comes at the price of less light hitting the sensor, so a longer exposure may need to be used.
Underwater Photography: An especially challenging area of photography requiring specialized equipment. At significant depth, the loss of light, color, and contrast become problems. Photographers routinely use flashes as well as wide-angle lenses to get as close as possible. Some cameras are specifically designed for underwater use, but most photographers use a traditional camera in a water-tight enclosures.
VR (vibration reduction) technology: This is what Nikon calls its image stabilization mechanism. It uses sensors to detect vertical and horizontal camera movement. It is coupled to small motors which move some of the lens elements to counter camera shake. The mechanism is activated when the shutter release is held down half way. If you do so, you can see through the viewfinder the huge difference it makes in real time. Nikon claims that you can shoot three to four shutter speeds slower and achieve the same results.
Remote shutter release: This enables an exposure to be taken without touching the camera (thus avoiding camera shake). With very long focal lengths, this becomes important. Remote shutter releases come in two flavors. Older cameras use a cable release, which is just a cable that plugs into the side of the camera and triggers the shutter. Many newer cameras use an infra-red remote control, which has the advantage of being able to be quite a distance away. This can be useful when taking self portraits. Many newer cameras have the option of using either a cable release or a remote control release.
Zoom Lens: A lens in which the photographer can vary the focal length between a pre-defined range. Thus, the photographer can make the image appear larger or smaller at will, without changing lenses. Nikon makes a lens with one of the largest ranges availible today - from 18 mm to 200 mm.
