Canon scanner CanoScan N656U User Manual
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91 Glossary Top Page Glossary Contents Index Grayscale Grayscale refers to a single-channel image made up of 256 shades of gray, ranging from white to black, that represent all tones in an image. Halftoning A method of simulating intermediate tones in black-and-white images by varying the patterns dots and lines. Halftoning is usually used for photographs, or other images with intermediate tones, scanned in Black and White. Height The Height text box contains the height of the current selection, or, if there is no selection, the maximum vertical output size, based on the currently selected Paper Size. Histogram The Histogram displays the distribution of bright and dark pixels for each color channel in the previewed image. The Eyedropper tool on the histogram graph lets you redefine the tonal profile. Keep Proportions button The Keep Proportions button affects the selection and the Width and Height text boxes. When you click the Keep Proportions button, the image size is maintained in the same proportion whenever you change either the width or the height. Low contrast An image that has low contrast does not have many distinct differences between tones.
92 Glossary Top Page Glossary Contents Index Mid-point The mid-tone portion of the image scanned as Color or Grayscale. When you click on the image with the Mid-point eyedropper, all tones between the black-point and white-point are adjusted in relation to the mid-point setting. Mid-tone Mid-tones are the middle range of tones in an image, between highlights and shadows. Midtones can be adjusted for color and grayscale images with the Gamma tool. moiré reduction Moiré reduction can be switched on with the Descreen button on the Scanner sheet. Moiré patterns are caused by poor dithering as a result of scanning images from published materials like newspapers, magazines, books, etc. When the Descreen feature is on, moiré reduction smoothes the overall appearance of the image and enhances image quality. OCR (Optical Character Recognition) OCR (Optical Character Recognition) software converts text images into actual text characters readable by a word-processing program or similar application. The Text Enhanced scan setting sharpens black and white contrast to assist in the accurate recognition of characters in OCR software. Optical resolution A scanners resolution capability. See also dpi, Resolution. Output Dimensions The final dimensions of the scanned image, based on paper size, cropping, and scaling.
93 Glossary Top Page Glossary Contents Index Output size The size of the acquired image, calculated by multiplying the width and height by the scale percentage. Overexposed An image that was exposed to too much light while it was being photographed. Paper Size An option on the Scanner sheet that determines the initial scanning area. Business card, Statement, B5, Executive, Letter, A4 and Full Platen are available. Pixel An acronym for picture element, a pixel is the smallest element used to create a screen image. It can contain up to 42 bits of color information. Platen The scanners document glass, where originals are placed for scanning. Preset Curves A set of curves designed to fix common photographic image problems such as underexposure, overexposure, or low contrast. Preview Area The area located to the left of the ScanGear CS-U main window where the image is displayed before the scan occurs. When you click the Preview button, the image on the scanner is scanned into the Preview Area, but not acquired by the application.
94 Glossary Top Page Glossary Contents Index Preview image cache When the preview image cache feature is switched on, the image in the Preview Area from the previous session with ScanGear CS-U is saved and displayed the next time ScanGear CS-U is launched from the parent software application. To switch this feature on and off, open the Preferences sheet for your scanner and click the button for “Display saved preview image”. Proportion The ratio of width to height. When you click the Keep Proportions button, the image size is maintained in the same proportion whenever you change either the width or the height. Resolution The degree of detail, translated into the number of pixels or dpi, which a device such as a scanner, video monitor, printer, or other image- displaying device, can display or reproduce. See also dpi, Pixel, Scan Resolution. Rotate Left The Rotate Left tool rotates the preview display 90 degrees counterclockwise. If the Preview Area is in portrait orientation, it becomes landscape and vice versa. Rotate Right The Rotate Right tool rotates the preview display 90 degrees clockwise. If the Preview Area is in portrait orientation, it becomes landscape and vice versa. Sampling In scanning, sampling is the process of measuring and recording the tonal or color value in an image and converting it to digital information.
95 Glossary Top Page Glossary Contents Index Scale The Scale setting lets you specify an output size for the selected image as a percent of the original width and height. Scan button Clicking the Scan button scans the original and sends it to the host software application. Scanner An input device that scans an original with a light source, and converts the image tones to digital information for computer applications. The digital information can be saved as a file, or converted to a text file using OCR software. Scan Resolution A list of preset levels of detail, expressed in dots per inch (dpi), for the scanned image, available from the Resolution list. See also dpi, Pixel, Resolution. Sliders On some of the controls in ScanGear CS-U, for example, the Contrast/ Brightness tool you click the slider and move it to the left or to the right to change the values. Statement A U.S. standard paper size measuring 5.5 x 8.5 in (139.7 x 215.9 mm). Status Bar The information line at the lower border of the ScanGear CS-U main window which provides helpful information about the current image and settings.
96 Glossary Top Page Glossary Contents Index Test Scanner button The Test Scanner button on the Scanner sheet starts diagnostic tests and reports if there are any problems with the scanner. Text Enhanced(OCR) A feature used by ScanGear CS-U to increase the accuracy of text scans. When Text Enhanced is selected for the Color Mode, images are scanned as Grayscale (8 bits per pixel) and converted to Black and White (1 bit per pixel) using Canon ImageTrust processing software. Threshold In a black-and-white image, the point at which a gray pixel is determined to become either black or white. The Threshold slider is on the Halftone sheet. Adjust the Threshold value when you are scanning a grayscale or halftone original with the Black and White setting. Tone Curve The curve displayed with the Tone tab tools to indicate the Black-, Mid-, and White-point tones in a color or grayscale preview image. You cannot edit the curve except with the Special Tone Curves tool. Tone sheet The Tone sheet contains tools that let you adjust and correct the image tone. The Tone sheet tools include Auto Tone, Contrast/Brightness, Gamma, Histogram, and Special Tone Curves. Toolbar A set of ScanGear CS-U tool buttons, located above the Preview Area, for image selection, orientation, and other basic adjustments.
97 Glossary Top Page Glossary Contents Index TWAIN TWAIN refers to an industry standard for transferring information from devices (such as a scanner or digital camera) to your computer. One interpretation of the acronym is Technology Without An Interesting Name. Underexposed A dark photographic image that was exposed to too little light when it was photographed. Unsharp Mask Sharpens an image, like a photograph that is slightly out of focus, by emphasizing the contrast to make outlines more clear. USB An abbreviation of Universal Serial Bus, an interface for external devices connected to a computer and easilly used simply by plugging and unplugging the USB cable while the computer is switched on. White-point The lightest portion of the image scanned as Color or Grayscale. When you click on the image with the White-point eyedropper, all tones lighter than the selected sample tone are adjusted to white. Width The Width text box contains the width of the current selection or, if there is no selection, the maximum horizontal output size, based on the currently selected paper size. Width-Height ratio Proportion of the image. To keep the width-height ratio intact, click the Keep Proportions button before changing the width or height values.
98 Glossary Top Page Glossary Contents Index X and Y Axes The X and Y axes on the Tone sheet curve chart represent, respectively, the input image color and output image color. Zooming Enlarging an image or a selected part of the image in the preview window or in a graphics application.
100 Index Top Page Glossary Contents Index A Advanced Mode defined ... 20 Main sheet ... 36 main window ... 23 scanning in ... 64 switching to Simple Mode ... 21 Auto Crop button ... 28 Auto Tone button ... 29 C Clear button function ...30 Color Mode Main sheet ... 36 Simple Mode sheet ... 32 ColorGear Profile Color Management sheet... 75 Contrast/Brightness button ... 41 Contrast/Brightness sheet ... 43 Crop button ... 27 D Descreen Scanner sheet ... 53 E Edit Image Type button Simple Mode sheet ... 34 G Gamma button ... 41 Gamma sheet ... 44 H Halftone sheet Threshold ... 51 Help opening on-line help ... 10 Help button ... 29 Histogram button ... 41 Histogram sheet ... 46