A customer walked into my shop last week complaining. She said, “ My camera isn’t working. I think there is something wrong with the chip.” I thought at first that the camera’s main computer wasn’t working and then I realized she was talking about her camera’s memory card, or the small picture storage hard-drive we insert in the camera. Digital technology confronts photographers with new terminology. I have written about terminology (or jargon) in the past, but for those new to this the following may help to understand just what some of the words mean.
Digital Images: The digital image is a grid of dots or picture elements (pixels). Each pixel is assigned tonal values (black, white, shades of gray, and color), the bits are then interpreted, read by the computer, and produced as an analog version for display or printing.
Pixel: Picture Element: Digital photographs are comprised of thousands, or millions of them; they are the building blocks of a digital photo (see above).
Sensors: When a picture is taken, the sensor is struck by light coming through the camera’s lens. Each of the tiny pixels that make up the sensor converts this light into electrons. The number of electrons, usually described as the pixel’s accumulated charge, is measured and then converted to a digital value. There are two most popular types: CCD: Charge Coupled Device; and CMOS: Complementary Metal-Oxide Semiconductor.
White Balance: Is a function on the digital camera. It refers to the relative intensity of colors in your image. Without correction, a picture taken at sunset can seem too yellow or orange and a picture taken under fluorescent lights might seem too green. Some cameras come with built-in automatic white balance correction.
DPI: Dots Per Inch is a measurement of the resolution of a digital photo or digital device. When printing, the higher the number the greater the print quality.
Image Resolution: Is the number of pixels in a digital photo and that affects the image quality.
LCD: Liquid Crystal Display: A low-power monitor often used on a digital camera to display settings or the photo itself.
Histogram: A graphic representation available on the LCD, of the range of tones from dark to light in a photo.
ISO: International Standards Organization is a rating describing the sensitivity of the cameras sensor to light. Generally, as ISO speed climbs, image quality drops.
JPEG: A standard for compressing image data developed by the Joint Photographic Experts Group. It is referred to as a lossy format, which means some quality is lost in achieving JPEG’s high compression rates. Usually, if a high-quality, low-compression JPEG setting is chosen on a digital camera, the loss of quality is not detectable to the eye.
RAW: Is the image format data as it comes directly off the sensor, with no in-camera processing.
Megabyte (MB): A measurement of data storage equal to 1024 kilobytes (KB).
Mega Pixel: Equal to one million pixels.
Noise: Pixels in your digital image that were misinterpreted, usually at the higher ISO values. It appears as random groups of red, green or blue pixels.
Shutter Lag: The time between pressing the shutter and actually capturing the image. This is due to the camera having to calculate the exposure, set the white balance, and focus the lens. It is usually a problem with small point and shoot cameras.