Scanning

1-bit
Another term for a line-art scan file or scanner setting. Refers to the number of bits (1) in the data. With one bit a pixel will either be black or white.
12-bits per color
A feature found in some desktop scanners. This feature allows the capture of much greater shadow detail (when compared with 8-bits) and allows the scanner to create a more satisfactory scan from an original that may be low in contrast.
24-bit Scanner
A 24-bit scanner can capture 8-bits of data in each of the red, green and blue colors.
36-bit Scanner
A 36-bit scanner can capture 12-bits of data in each of the red, green and blue colors. The data will be analyzed and dropped to 24-bits of data but through this process, image quality is enhanced.
8-bit
Another term for a Greyscale scan file or scanner setting. Refers to the number of bits (8) in the data. With 8-bits per pixel the image will have 256 shades of grey. This is a sufficient number of grey values to create a quality black and white photographic reproduction.
Bitmapped Image
A bitmapped image is a computer file representing a line-art image that was scanned with a scanner. Refers to the pattern (map) of bits that are either black or white.
Black Point Adjustment
An adjustment made that will determine the amount of shadow detail in an image. It is considered proper to set the black point so that the darkest part of an image will only just have zero detail.
Brightness Adjustment
An adjustment on a scanner that allows the user to compensate for a light or dark original.
CCD
Stands for Charge Coupled Device. Essentially a light sensitive computer chip, a CCD is the optical element in a CCD scanner that converts light to voltages. The more light a CCD receives, the higher voltage it creates. These voltages are converted by the scanner into the images we see.
Color Correction Adjustment
The act of correcting for and eliminating an unwanted color cast. Part of the scanner set-up, a preview image is measured on the computer display and adjusted so that the color measures in the desired way. After this adjustment is made, the actual scan is performed using these color correction settings.
Color Space
A color space is a particular language used to describe color. Examples of color spaces are: RGB, CMYK, HSB, CIE LAB.
Contrast
The range between lights and darks in an image. Proper contrast is important so that an image appears realistic.
Contrast Adjustment
That act of adjusting contrast for proper visual results.
Curve
As in tone curve, or color correction curve. Beginning as a 45° angle line running up to the right, this line is adjusted into a curve shape by the user to effect color or tone correction. The lower left end of the curve typically represents the dark portions of a picture and an upward bend will typically lighten the shadows. Similar capabilities exist by working with the middle or highlight parts of the curve. In this way it is possible to alter only certain tone ranges of an image without making un-wanted changes in other parts of the image.
DPI
An improper expression of the resolution of a scanned image. The expression pixels per inch (PPI) is the correct indication of scanned image resolution. DPI (standing for dots per inch) is used in expressing the resolution of a laser printer or other output device.
Drum Scanner
A type of scanner on which original artwork is attached to the outside of a spinning glass drum. The image is scanned by photo multiplier tubes (PMTs) and is captured to a disk file. This type of scanner gives the best quality result.
Dynamic Range
An expression of the density difference between highlights and shadows. As a measurement of scanner quality, dynamic range is one of the primary differences between low and high quality scanners. A desktop scanner with a small dynamic range will yield scanned images that lack detail in shadow areas.
Flatbed Scanner
A type of scanner with a light sensing CCD element on a moving carriage mounted under a sheet of glass. Artwork is placed face down on this glass and covered with a hinged cover. A flatbed scanner has much in common with the top portion of an office copier.
FPO Scan
A low-resolution photographic scan (usually 72 PPI) used for composition purposes only. After laser hardcopy is produced, the FPO image is replaced with a different (high-resolution) scanned image.
Gradation Adjustment
An adjustment leading up to performing a scan where the user makes adjustment to the brightness and color balance of the image. After performing a preview scan, the user will adjust the tone correction curves of their scanner to achieve natural color.
Grayscale Image
A term for a black & white photographic scan file. Refers to the range of 256 grey tones that make up the image.
Grey Balance Adjustment
A color correction adjustment to insure that grey elements within a scanned image appear as a neutral grey. It is generally considered proper technique to adjust the image so that neutral grey elements appear neutral gray. If this is done, it will usually be true that other elements within the image will also have true color reproduction.
High-resolution Image
A term used to describe an image with enough detail (achieved through having plenty of pixels per inch) for quality reproduction and use in final film. How high the resolution should be depends on the image type: Line-art should have resolution of 600 PPI or above and photographs should have resolution twice the anticipated halftone screen frequency.
Interpolation
A function found on low cost scanners where optical resolution (expressed as PPI) is enhanced through software enhancement. In this way, a 300 PPI scanner can create 600 PPI files. Interpolation does not give as good a result as a scanner with higher optical resolution. (The software won't be able to enhance detail the scanner doesn't see in the first place.)
Low-resolution Image
A low-resolution photographic scan (usually 72 PPI) used for composition purposes only. After laser hardcopy is produced, the low-resolution image is replaced with a different (high-resolution) scanned image.
OPI
Open Prepress Interface. A term relating to the use of special low-resolution versions of high-resolution images. This process offers faster page layout. These low resolution images are automatically exchanged for the high-resolution version when the layout is output.
PhotoCD
A technology from Kodak that allows photographic images to be stored on a CD-ROM disc. These PhotoCD images can be displayed on a television set or can be used in a desktop page layout and separated to film. A complex technology, the achievable quality depends on a talented computer operator with knowledge of color prepress techniques. That in hand, PhotoCD can achieve above average quality color separations for a low unit cost.
Pixel
The smallest building block within a scanned line-art or photographic image. A pixel is the small square picture element that is filled with a color, or black or white. Pixels come in various sizes and their size is expressed in terms of resolution. Resolution is measured in pixels per inch (PPI.)
PMT
Photo Multiplier Tube. A light sensing element used in high quality drum scanners. It is said that scanners using PMT technology create the highest quality scans.
PPI
Pixels Per Inch. An expression of resolution of a scanned image.
Resolution of a Scanner
Expressed as PPI (pixels per inch.) The resolution of a scanner limits the enlargement capabilities of the device. Optical resolution is the resolution of the device and interpolated resolution is resolution enhanced by software and is the res. frequently touted in scanner advertisements. Interpolated resolution does not always yield significant detail enhancement.
Shadow Detail
A term that refers to the amount of detail contained in the dark parts of an image. It is desirable to maintain shadow detail but there is a risk of decreasing overall contrast if one lightens the shadow too much in an attempt to expose detail. If an image is scanned without shadow detail, it will be impossible to regain detail in an image editing program.
Sharpness
An attribute of a scanned image and also an attribute of a good quality scanner. It is considered desirable for an image to have good sharpness.
Tone Curve
A term for an adjustment available on certain scanners. Beginning as a 45° angle line running up to the right, this line is adjusted into a curve shape by the user to effect color or tone correction. The lower left end of the curve typically represents the dark portions of a picture and an upward bend will typically lighten the shadows. Similar capabilities exist by working with the middle or highlight parts of the curve. In this way it is possible to alter only certain tone ranges of an image without making un-wanted changes in other parts of the image.
Unsharp Masking
An important function that allows the user to add apparent clarity via electronic means. Unsharp masking is considered the most sophisticated sharpening method because it sharpens without the undesirable graininess that appears with other sharpening methods.
White Point Adjustment
An adjustment made that will determine the amount of highlight detail in an image. It is considered proper to set the white point so that the lightest part of an image will only just have zero detail.