Photography Concepts and Terminology

Auto Exposure AE - When the camera automatically sets the shutter speed, aperture and white balance, known as:
  • Program Mode - The camera chooses shutter speed and aperture automatically, usually with a shutter speed of a 60th of a second or higher.
  • Aperture Priority - The camera automatically chooses shutter speed according to lighting conditions, while you manually choose the aperture in order to control the depth of field (background in or out of focus).
  • Shutter Priority - The camera chooses the correct aperture according to current lighting, while you choose the shutter speed, for example, for sports shots. 
Auto Exposure AE Lock - Press the shutter half way down in order to lock in an exposure reading, allowing you to re-frame the shot while maintaining the original exposure setting. 

Auto Focus AF -  The camera lens automatically focuses on what it perceives to be the focal point. You may have to move the camera in order to focus on what you really want.

Aperture - The camera lens opening that allows light onto the photo sensors. The aperture is measured in f-stops, which are numbered inversely, so the larger the aperture, the lower the number.

Aperture Priority AE - The camera automatically chooses shutter speed according to lighting conditions, while you manually choose the aperture. A large aperture, f/2.8, will let in more light resulting in a narrow depth of field, which is the field of focus, so objects in front or back will be blurry. A small aperture, f/22, will not let much light in, giving greater depth of field, with more in focus. Small apertures will require brighter light in order to deliver a faster shot.

Automatic Exposure -  The camera sets the shutter speed and aperture for the correct exposure according to the light.

Automatic White Balance AWB - The camera adjusts for ambient light, whether outdoor, incandescent, fluorescent, etc.

Backlit  - When the light source is behind the subject. This can result in underexposure. 

Bracketing - A process to evaluate exposure by taking three photos - automatic, underexposed, and overexposed.  Also called "exposure bracketing".

Brightness - Value of a pixel in a digital image giving its value of lightness from black to white, with o being black and 255 being white.

Charged Coupled Device CCD -  Converts light waves into an electric charge and processes it into an electronic, digital format that can be saved on flash memory. 

Channel - One piece of color information stored in a 3-channel red, green and blue image. 

Chroma - Chroma in an image element is composed of saturation (color depth) plus hue (a particular color), but does not include luminance (intensity of light).

CMOS - Complementary Metal Oxide Semiconductor is an imaging system used by digital cameras using less power than CCDs with higher image quality. Usually found in higher-end cameras.

CMYK -  Cyan, Magenta, Yellow and BlacK. Color code based on the pigments used by most printers. Since your camera and computer display use RGB color, color shifts may occur when your color management system tries to convert RGB files to CMYK. 

Color Balance - The accuracy with which an image matches the original colors.

Compression - Image files of all kinds are notoriously large, so they are compressed according to algorithms such as JPEG, in which some color information is lost (lossy) in order to take up less space. RAW, BMP and TIFF files do not use compression (lossless) and take up more space. GIF files have limited color channels and take up less space accordingly.

Contrast - The rate of change of brightness in an image.

Depth of Field DOF -  The range of focus in an image as a result of  focal length and aperture opening of a lens. A large or wide aperture (f-stop) gives a shallow depth of field (narrower range in focus) and a smaller aperture (f-stop) gives a large depth of field  (wider range in focus).

Digital Zoom - Increasing the center 50% of an image by using interpolation, or "guessing" what the extra pixels ought to be. Optical zoom is based on actual lens capacity and is superior to Digital Zoom.

Dots Per Inch DPI - The resolution of a screen display or printer based on the number of pixels, or picture elements

Digital Single Lens Reflex DSLR -  Higher-end camera with manual settings and interchangeable lenses.

Exposure Value EV -  The camera sets the Aperture and Shutter Speed, but allows manual setting of the exposure in order to under- or over-expose the image. 

Exposure - Amount of light that hits the photo sensor, depending on shutter speed and aperture.

F-Stop - Number that indicates the size of the aperture, or opening in the camera that lets light in. It is an inversely proportional number, for example, f/2.8 is a large opening and f/16 is a small opening.

Flash Memory - Equivalent to film for digital cameras. Saves data and is re-writable. SD, Secure Digital cards are the most commonly used type of Flash Memory.

Focal Length - Angle of a lens view, whether wide angle, standard or telephoto.

Focus Assist - Cameras  send out normal or infrared light to assist with the auto focus in low light situations

Focus Lock - Pressing the shutter half way down to focus on the subject and then re-frame by moving the camera for more control over focus. The camera will then take a picture with less shutter delay.

Gamma Correction -   Adjust overall brightness according to the human eye's perception of midtones in an image.

Gamut - The range of colors available in an image process. Often refers to the capabilities of a printer to reproduce color accurately.

GIF -  Graphics Interchange Format, mainly used for internet graphics or small animated files. Not good for photographs since it contains a maximum of 256 colors.

Grayscale - Refers to black and white photography, including shades of gray.

Histogram - A graphical representation of current light and color distribution for a given image.

Hue -  Hue is the color you are currently using out of the complete range of colors of the spectrum. 

Image Sensor -  Digital cameras use an electronic image sensor (CCD or CMOS), to gather the image data, whereas a traditional camera exposes light to emulsion film.

Image Stabilization IS -  Optical or digital technology that reduces camera shake.  It is most effective with telephoto zoom lenses, which are heavy and often unsteady. 

International Standards Organization, ISO -  Originally based on emulsion film's sensitivity to light, ISO classified film according to numbers 100, 200, 400, 800 and 1600. The higher the number, the more sensitive to light and thus greater capacity to take fast pictures. Using the higher ISO speeds in digicams will result in a grainier image.

JPG, JPEG -  The most common type of compressed image file format. The compression causes unavoidable loss of color data, so it is considered "lossy." JPEG 2000 features higher compression with less image quality loss.

Megabyte MB -  Memory term referring to 1024 kilobytes. Flash memory cards hold multiples of this as 4MB, 8MB etc. 

Megapixel  MP -  The image sensor resolution of 1 million pixels. Digicams are commonly rated by how many megapixels their sensor capacity. For a total pixel count, multiply the horizontal resolution by the vertical resolution to get the total pixel count i.e., 2590 x 1920 = 5 Megapixels.

Metering -  Calculates the exposure from the existing light conditions, using modes such as Matrix Metering, Multi-Pattern Metering, Spot metering and Center-weighted metering.

Noise - Pixels beyond the reach of your camera's sensors, often occurring in long exposure or high ISO shots. 

Optical Zoom - Mechanical, not "digital" multi focal length lens, and thus of better quality. 

Panorama - A series of images you can "stitch" together into one wide picture using special software.

Pixel - A picture element produced by a photo sensor. Higher numbers mean higher resolution.

Pixelization - When an enlargement begins to show the The stair stepped appearance of a curved or angled line in digital imaging. The smaller the pixels, and the greater their number, the less apparent the "pixelization" of the image. Also known as the "jaggies". Anti-alias software attempts to minimize pixelization.

Resolution - The number and/or size of pixels, or picture elements, used to create the image. More, smaller pixels add detail and sharpen the edges.

Red Green Blue RGB -  Primary colors of the light spectrum. The "additive" reproduction process mixes various amounts of red, green and blue to produce the secondary colors cyan, magenta and yellow. Combining all three produces white.

Saturation -  The depth of color hue, or degree to which a color is undiluted by white light. If a color is 100 percent saturated, it contains no white light. If a color has no hue saturation, it is a shade of grey.

Scene Modes -  Pre-programmed scene settings that suit the current shooting conditions. The camera will automatically change the settings whether Portrait, Sports, Night,  Musem, etc.

Secure Digital SD -  A flash memory card used in many digicams, handhelds, and MP3 players.

Shutter Lag -  The time needed by the camera to calculate settings between pressing the shutter and actually capturing the image. Higher end DSLRs with mechanical (not electronic) shutters have virtually no shutter lag.

Shutter Priority AE -  Manual setting of the shutter speed while the aperture setting is automatically determined by lighting conditions.  A fast shutter speed stops fast action, while a slow shutter speed results in the blurring of a fast-moving subject. Shutter priority is often used for sports or wildlife photography.

Telephoto -  A long, narrow-angle focal length lens that bring distant objects closer.

Time-Lapse -  Photographing an image at preset intervals. Also known as Interval Recording or Intervalometer.

Technology Without An Industry Name TWAIN - Protocol for exchanging information between software and  devices such as scanners and digital cameras. 

Universal Serial Bus USB -  Port and cable for transferring data from the camera to computer

White Balance - Adjustment of the brightness of the red, green and blue components, so that the brightest object in the image appears white. Used to compensate for different light sources which may give a color cast to a photo, whether green, orange, yellow, blue etc.

Wide angle - Lens focal length that is normally much smaller than a normal lens, allowing more of an area to be included in a picture. Closer objects may appear quite large while objects farther away will appear tiny.

Zoom Lens  - A variable focal length lens. Most point and shoot digicams include an optical zoom of up to 5X, but zoom lenses from 10X to 12X or higher add at least $50 - $100 to the cost of a fixed lens camera. 

Also see:

Photography Concepts from Cambridge Colour

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