Basic Terms in Digital Photograhy

[from Webopedia]

aperture [光圈]
A device that controls the amount of light admitted through an opening. In photography and digital photography, aperture is the unit of measurement that defines the size of the opening in the lens that can be adjusted to control the amount of light reaching the film or digital sensor. The size of the aperture is measured in F-stop.

depth of field [景深]
Abbreviated as DOF, depth of field is a unit of measurement that represents the range of distances within an image where the focus is acceptably sharp.

digital camera [數位相機]
A camera that stores images digitally rather than recording them on film. Once a picture has been taken, it can be downloaded to a computer system, and then manipulated with a graphics program and printed. Unlike film photographs, which have an almost infinite resolution, digital photos are limited by the amount of memory in the camera, the optical resolution of the digitizing mechanism, and, finally, by the resolution of the final output device. Even the best digital cameras connected to the best printers cannot produce film-quality photos. However, if the final output device is a laser printer, it doesn't really matter whether you take a real photo and then scan it, or take a digital photo. In both cases, the image must eventually be reduced to the resolution of the printer.
The big advantage of digital cameras is that making photos is both inexpensive and fast because there is no film processing. Interestingly, one of the biggest boosters of digital photography is Kodak, the largest producer of film. Kodak developed the Kodak PhotoCD format, which has become the de facto standard for storing digital photographs.
Most digital cameras use CCDs to capture images, though some of the newer less expensive cameras use CMOS chips instead.

digital photography [數位相片]
The art and science of producing and manipulating digital photographs -- photographs that are represented as bit maps. Digital photographs can be produced in a number of ways:
· Directly with a digital camera
· By capturing a frame from a video
· By scanning a conventional photograph
Once a photograph is in digital format, you can apply a wide variety of special effects to it with image enhancing software. You can then print the photo out on a normal printer or send it to a developing studio which will print it out on photographic paper.
Although the resolution of digital photos is not nearly as high as photos produced from film, digital photography is ideal when you need instant, low-resolution pictures. It's especially useful for photos that will be displayed on the World Wide Web because Web graphics need to be low resolution anyway so that they can be downloaded quickly.

focal length [焦距]
In digital photography and digital video recording, the focal length refers to the size of the image and angle of field of view as seen by the camera through the lens. This is the center of the lens to the image pickup device.

focus spread [焦寬=景深]
See depth of field

F-stop
In digital photography and digital video recording, F-stop refers to the international standard sequence of numbers that express relative aperture. F-stop is the "lens focal length" divided by the "effective aperture diameter." The smaller the F- number, the greater the amount of light that passes through the lens. Each change of F-stop halves or doubles the image brightness as you step up or down.

optical resolution [光學解析度]
The physical resolution at which a device can capture an image. The term is used most frequently in reference to optical scanners and digital cameras. In contrast, the interpolated resolution indicates the resolution that the device can yield through interpolation -- the process of generating intermediate values based on known values. For example, most scanners offer an optical resolution of 300 dpi, but an interpolated resolution of up to 4,800 dpi. This means that the scanner can actually capture 90,000 pixels per square inch. Then, based on the values of these pixels, it can add 15 additional pixels in-between each pair of known values to yield a higher resolution.

shutter [快門]
In photography and digital photography applications, the shutter is the device on the camera that opens and closes to control how long the focal plane is exposed to light. On a video camera there is no physical shutter, instead the camera CCD samples light for an appropriate length of time, and then shuts off.

shutter speed [快門速度]
In photography and digital photography the shutter speed is the unit of measurement which determines how long shutter remains open as the picture is taken. The slower the shutter speed, the longer the exposure time. The shutter speed and aperture together control the total amount of light reaching the sensor. Shutter speeds are expressed in seconds or fractions of a second. For example 2, 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000, 1/8000. Each speed increment halves the amount of light.


SLR [單眼相機]
Short for single lens reflex, it a term associated with cameras and digital cameras. SLR cameras use a mirror between the lens and the film, or image sensor, to provide a focus screen. This means the image you see in the viewfinder (or LCD) will be the same as what appears on film or as your digital image.

zoom lens [伸縮鏡頭]
In digital cameras and digital video recording device, a zoom lens let you to select any focal length within the len's range. The lens changes the angle of view and its magnifying power based on the zooming range selected.
Zooming out gives the photographer a wide-angle view that captures a wide expanse of a scene. When you zoom in, the field of view narrows and you can focus on small portions of the scene without having to physically moving closer.