Digital Scanning & Microfilm Equipment – DS & ME
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Digital Dictionary – A Glossary of Photographic Terms Photo Review – Digital Imaging Glossary Jisc Digital Media – Glossary Astrophotography by Jerry Lodriguss- Glossary of Digital Imaging Terms Usability, etc. – A Glossary of Image Processing Terms WebJunction – Glossary of Scanning and Digital Imaging Terms Xerox Corporation – Scanners – Glossary of Terms Motorola – Glossary of Terms – Scanner Glossary On reviewing the information listed below related to this product you may find that you wish to request a Quotation for evaluation. If you require a written quotation then please Contact Us @ DS & ME should you require a Quotation and we will respond to your request at the earliest opportunity. Additional input and additions to the above source material has been created and inserted by Laurie Varendorff ARMA – due to the dated nature of some of the information provided based on his 40 years experience in the microfilm, micrographics and microforms industry. In addition to the terminology provided on this page several of the National and International Standards Organisations provide, at a charge, more detailed lists of terms than appear in this listing. The Standards Organisation and the Document Number for their offerings, when available, are listed below. The standards organisations and the document number for their offerings, when available, are listed below.
1-bit Black & White: ( Monochrome ) Scanning an item where the resulting image is in black or white, each pixel in the image is either on or off.
There are no intermediate shades of grey to offset black or white. This scanning method produces the smallest file size.
8-bit Greyscale: Scanning an item where the resulting image contains 256 possible shades of grey.
This is 256 possible intensities of the color grey when converting a color image into a greyscale image.
24-bit Color: ( True Color ) Scanning an item where the resulting image contains a possible 16 million distinct colors.
24-bit color images are composed of three 8-bit color channels.
Each color channel, similar to an 8-bit grayscale image, contains up to 256 colors.
When combined, the red, green and blue channels provide up to 16.7 million colors.
24-bit color is also known as True Color and Photo-realistic Color.
This is the industry standard for the threshold where the human eye can recognize distinct color variations.
This method of scanning produces the largest file size.
32-bit color: 32-bit color images have 4 color channels of 8 bits each – one channel each for red, green and blue, plus 8 bits of grayscale data to provide higher detail.
A/D converter: A device used to convert analog data to digital data. Analog data is continuously variable, while digital data contains discrete steps. Additive primaries: Red, green, and blue light that, together, produce white light. These are the primary colors of light from which all other colors can be made. Compare with subtractive primaries.
AE: Auto Exposure. When the camera is set to this mode, it will automatically set all the required modes for the light conditions. I.e. Shutter speed, aperture and white balance. The 3 types are:
1. Program Mode: The camera will choose the shutter speed and aperture automatically, effectively making your SLR a “point-and-shoot”. It will normally assign a shutter speed of 60th of a second or higher if possible. 2. Aperture Priority: You choose the aperture setting and the camera will automatically choose the shutter speed according to the lighting conditions. Best setting for controlling the depth of field. 3. Shutter Priority: You choose the shutter speed and the camera will select the correct aperture as long as there is enough light. Good for sports or action photography where you need control over the shutter speeds.
AE Lock: This enables you to lock the current exposure reading and re-frame the shot using the same setting.
A half-press of the shutter is normally required to activate this function, fully pressing only when you want to capture the image.
AF: Auto Focus. All digicams and most modern SLR lenses have this function now.
The lens automatically focuses on the subject as quick as the eye. The only difference is that with an SLR you can normally select manual focus if necessary.
Aliasing: Aliasing occurs when there are sharp contrasts between two side-by-side color or greyscale pixels producing visible jagged lines along an angled edge.
This jagged line separation often looks like a series of steps going up the line.
Alpha channel: An 8-bit channel reserved by some image-processing applications for masking or additional color information.
Angle of View: This is calculated by the focal length of the lens and the size of the image sensor.
The 35mm equivalents differ according to the sensor size.
Anti-Aliasing: Anti-aliasing is a process that smooths edges during the scanning capture process so that there is a more gradual pixel change than that which is being captured.
The result is the final scanned image looks like the original rather than having a sharp contrast causing jagged lines.
Aperture: The lens opening that allows more, or less light onto the sensor formed by a diaphragm inside the actual lens.
Aperture Priority AE: When using this mode, the user selects the aperture giving control over the Depth of Field.
A large aperture letting more light in gives a small depth of field, meaning not much will be in focus.
Whereas a small aperture, not letting much light in, will give a greater depth of field or more will be in focus from the front to back of the image.
Archive: A collection of data in long term storage, usually the hard drive on your PC or an external hard drive.
Array: An ordered collection of elements of the same type.
Represented by single line of sensors in a CCD chip are called a linear array.
A digital image is stored as a 2-dimensional data array containing pixels addressable by x, y ( or row, column ) coordinates.
Artefact: A visible indication ( defect ) in an image, caused by limitations in the reproduction process.
ASCII: ( American Standard Code for Information Interchange ) Standard by which many computers assign code numbers to letters, numbers and symbols.
Used for text exchange between computer platforms.
Aspect Ratio: The ration of horizontal to vertical dimensions of an image.
For example, 35mm slide film = 3:2, TV = 4:3, HDTV = 16:9, 4×5 Film = 5:4.
Aspherical Lens: A lens with edges flattened so that it is not a perfect sphere. These produce a much superior image.
Automatic Exposure: The camera sets the shutter speed and aperture for the correct exposure according to the light.
Automatic Focus: The lens on the camera focuses automatically when the shutter is half pressed.
The viewfinder normally has focussing points shown to assist the user in knowing what will be in focus.
AVI: Movie clip in Windows AVI format.
A lot of digicams now have this feature for producing small video clips.
AWB: Automatic White Balance.
Most digital cameras have this feature where the camera sets the white balance.
Override is available in most DSLR’s.
B & W: Abbreviation for Black and White.
Back Lit: Meaning the subject is lit from behind which can cause underexposing.
Is also used for portrait photography for special effects and bringing catchlights to the hair.
Backlight: The illumination for a colour LCD display on digital cameras or phones.
Banding: An artefact of colour gradation in computer imaging.
When graduated colours break into larger blocks of a single colour, the smooth look of a proper gradation is reduced.
A visible stair-stepping of shades in a gradient.
Barrel Distortion: A common geometric lens distortion causing an acquired image to pucker towards the centre and be rounded along the outer edges.
Batch Scanning This refers to the type of documents being scanned.
If multiple sets of paper are being scanned but each set of documents needs to be in a separate soft-copy file then each set is referred to as a batch.
Additional information on Batch Scanning is available from Digital Scanning & Microfilm Equipment – DS & ME @ Digital scanning & Microfilm Equipment – DS & ME
Bezier curves: In object-oriented programs, a curve whose shape is defined by anchor points set along its arc.
Bi-level: A type of image containing only black and white pixels.
Binary: Binary, or base 2, is a numbering system with only two digits, 0 and 1.
Binary is convenient for use with bits which have only two states, on and off.
Bit: ( Binary digit ) The smallest number in digital data and is either 1 or 0 representing either on or off.
Also See Byte
Bit depth: The bit depth of the scanner is the internal color sampling.
The bit depth of a scanner may have a higher listing than the output range.
For instance, many flatbed scanners may have a 32-bit color, or higher, internal bit depth color sampling but the output will in 24-bit ( True Color ).
This means that the scanner is capturing as much information as possible but only outputting the best 24-bit colors.
Some scanning applications, such as Adobe Photoshop, have an option for scanning with the output as the scanner maximum.
Depending on the scanner model the possible bit depth output will be the same as the internal bit depth specification.
Please refer to the scanner specification for the bit depth information.
The same is true for the greyscale bit depth internal sampling.
The Visioneer 9520 scanner, for example, has a 42-bit color sampling and a 16-bit greyscale internal sampling.
Also See 8-bit greyscale and 24-bit color
BMP: ( Bitmap ) Graphics file format used in Microsoft Windows.
Is the basic and default picture file type from the Microsoft Paint program.
There is no compression of the image therefore no loss of image clarity and as a result, .bmp files tend to be much larger in size.
While a .jpg” file may only be 600 KB the mirrored un-compressed .bmp file could be 6 MB.
Generally it is best to scan as a BMP if additional image processing is to be done.
An image formed by rectangular grid of picture elements ( pixels ).
The computer assigns a value to each pixel, from one bit of information ( indicating black or white ) to 24 bits per pixel ( for full-color computer displays ), to as many as 64 bits per pixel for some types of full-color images.
A bitmap is an image defined by a collection of dots, as opposed to a vector image, which is defined by mathematical formulas.
Black & white: Refers to both line art and halftone bitmapped image types.
Black point: A movable reference point that defines the darkest area in an image, causing all other areas to be adjusted accordingly.
Brightness: Brightness refers to the lightness or darkness of the image.
Brightness is one of the three dimensions, with saturation and hue, in color space settings.
If the brightness is set to 0% then the resulting image will be completely black.
If the brightness is set to 100% then the resulting image will be entirely white.
Also See Color Hue Color Saturation and Gamma
Buffer: Temporary storage areas held in your camera or computers RAM.
This acts as a temporary holding area for data that will be manipulated by the CPU before saving it to another device.
For example if you are shooting in continuous mode, when the RAM buffer on your digital camera is full it will slow to a much slower rate while the buffer empties to your compact flash card or other device.
Byte: A byte is generally 8 bits of data. A kilobyte ( KB ) is 1024 bytes of data, often rounded to one thousand bytes of data.
The standard unit measure of file size.
A megabyte ( MB ) is 1024 kilobytes or one million bytes of data.
A gigabyte ( GB ) is 1024 megabytes or one billion bytes of data.
When the computer industry references speed of transfer or storage of data it usually is indicating either the bit or byte transfer speed or storage size.
In general, a megabit is indicated as Mbit and a megabyte is indicated as MB.
Therefore, 480 Mbit per second transfer rate is 480,000,000 bits per second or 57 MB per second.
Also See Bit
Calibration: The process of measuring dark / light and beginning / end so that the output image is of the same quality of the input image.
Setting equipment to a standard measure to produce reliable results.
With the strobe sheetfed scanner family this is a manual process, using a black and white calibration page on install.
Recalibration for this family of scanners should be completed any time black lines appear in the scan.
Also See Sheetfed Scanner
Calibration bars: On a negative, proof or printed piece, a strip of tones used to check printing quality.
Card Reader: Used for transferring data from your flash memory card to your PC.
A better way of transferring your image files than connecting the camera to your PC.
Sometimes the cameras circuitry can become corrupt.
Better to fry a memory card than your camera.
CCD: A charge-coupled device, or CCD, is a light sensitive electronic device that converts light into an electrical charge.
CCD Array: ( Charged-Coupled Device ) The core component of the scanner head that captures the image of the item being scanned after the image is reflected into the array by the last mirror in the scanning head.
A diode that is light-sensitive when charged with electrical voltage.
Also See Scanner and Scanning Head
CD: Compact Disc. You should have heard of these by now.
Storage media capable of holding around 650 MB of data.
These come in 2 forms;
1. CDR: Compact Disc Recordable. Can only be used once, no matter how little information you write to it. Can be re-read many times. 2. DR-W: Compact Disc Re-writeable. This can be erased and re-used many times.
CF: Compact Flash card. Used in your digital camera to record images. Storage space ranges from 16MB up to 12GB.
A company in Japan is currently developing a CF card that will store 2TB of information or 2,048 Gigabytes.
Channel: One piece of information stored with an image.
For example, a true colour image has 3 channels, red, green and blue.
Chroma: The colour of an image element or pixel.
A Chroma is made up of saturation plus the hue values, but is separate from the luminance value.
Chromatic Aberration: Also known as purple fringing. It is fairly common in 2 MP digital cameras and above, especially if they have long telephoto lenses.
You can see it when a dark area is surrounded by a highlight.
In between the dark and light, you may see a band of purple pixels that shouldn’t be there.
There are ways of removing this which I have covered in the Photoshop section.
CIE: ( Commission Internationale de l’Eclairage ) An international group that has developed a set of color definition standards endorsed by Adobe for PostScript Level 2.
CIFF: Camera Image File Format. This is an agreed type of image storage used by many camera makers.
CMOS: Complementary Metal Oxide Semiconductor ( now you can see why it is abbreviated ) – Another imaging system used by digital cameras.
These produce lower amounts of power consumption, but are not as popular as the CCD sensors used in most digital SLR’s
CMS: Colour management system. A software program designed to ensure colour matching and calibration between video and / or computer monitors and any form of hard copy output.
This ensures color uniformity across input and output devices so that final printed results match originals.
The characteristics or profiles of devices are normally established by reference to standard 1T8 color targets.
CMYK: ( Cyan, Magenta, Yellow and Black ) Colours used by most printers to produce your prints.
Colour shifts can be caused when the colour management system tries to convert your PC’s RGB files to CMYK.
Before printing, try converting your images to CMYK and see what the difference is.
Codec: A Codec compresses information to enable it to be sent across a network much faster.
It will also decompress information received via the network.
Colour Balance: The accuracy with which the colours captured in the image, match the original scene.
Colour Cast: This is a very unwanted tint of one colour in an image caused by the wrong amount of Cyan, Magenta and Yellow.
An overall color imbalance in an image, as if viewed through a colored filter.
It can be corrected using your editing software.
Colour Correction: To correct or enhance the colours within an image.
Colour Depth: Digital Images can approximate colour realism but the process is referred to as colour depth, bit depth or pixel depth. Most modern computer displays use 24 bit true colour.
It displays the same number of colours that the human eye can discern, about 16 million.
Colour Space: Digital cameras use known colour profiles to generate their images.
The most common is sRGB or Adobe RGB.
This along with all of the other camera data is stored in the Exif header of the Jpeg file.
The colour space information ensures that graphic programs and printers have a reference to the colour profile that the camera used at the time of taking the exposure.
Compact Flash: See CF. This is the most commonly used type of memory.
It is small, removable and available in a wide range of sizes up to 12 GB.
Compression: A Digital photograph creates an image file that is enormous.
Encoding the bits of information in an image file so that it takes up less space when stored.
Compression results in little or no distortion.
To enable image files to become smaller and more manageable cameras employ some form of compression such as JPEG. RAW and TIFF files have no compression and take up more space.
Also See - Lossy and Non-lossy
Continuous Autofocus: As it says.
The auto focus system is continuously working on focussing on the subject.
Continuous-tone: Image that has a complete range of tones from black to white: photographs, paintings and drawings.
Negative or positive with a broad range of tones that have no screened dots.
Contone: ( CT ) An abbreviation for continuous tone. A color or grayscale image format capable of illustrating continuously varying tonal ranges, as opposed to line art.
CT is also the name of a file format used for exchanging high-level scan information.
Contrast: Contrast is the range between the darkest and lightest portions of the image.
Lowering the contrast will make the image appear fuzzier as the separation between light and dark pixels is lowered.
Raising the contrast will make the separation between light and dark more intense.
The higher the contrast the more the separation between pixels will appear as jagged lines which are seen in aliasing.
Crop: Cropping an image refers to removing the excess information that is surrounding the digital image of the original document.
For instance, the most standard photo size is 4 x 6 but if these photos were measured they are generally 3.95 x 5.95.
Choosing to crop an image will remove the fraction of an inch additional white or black that may be in the resulting image.
Also See “Auto-Crop”
Crop marks: Lines printed showing the dimensions of the final printed page.
These marks are used for final trimming.
CRW: The RAW CCD file format used by Canon Digital Cameras. Comes from Canon RAW.
CSV: ( Comma Separated Value ) .csv is a common file type which can be imported into spreadsheet applications such as MS-Excel, database applications such as MS-Access, and contact databases such as MS-Outlook, ACT, Goldmine, etc.
This file type stores data in a spreadsheet type file where each cell in the file contains one piece of data such as first name, last name, address, etc
DC: Direct Current. Battery power such as 9v DC battery
Data compression: “Squeezing” of data for the purpose of transmission throughput or storage efficiency.
Portions of the data are removed using an algorithm that will restore the data when needed.
Decompression: The expansion of compressed image files.
Also See Lossy and Non-Lossy
Default: Command or parameter that takes effect if no other option is specified.
Densitometer: A measuring instrument that registers the density of transparent or reflective materials.
It is used to check the accuracy, quality, and consistency of output.
Colors are read as tonal information.
See also Colorimeter and Spedrophotometer
Density: The ability of a material to absorb light.
Measure of the light transmission of a transparent or translucent object or the light-absorbency of a reflective surface.
In photography, measurement of the opacity of a transparent or translucent object.
On a film negative, the greater the density area, the more black or more developed it is.
Density is measured from 0 to 4.0.
It is calculated by measuring the reflectance or transmittance of light and calculating theoretical light absorption.
Depth of Field: ( DOF ). The range of items in focus in an image.
This is controlled by the focal length and aperture opening of a lens.
A large or wide aperture gives a shallow depth of field ( not much range in focus ) and a smaller or narrow aperture give a large depth of field ( more range in focus ).
Descreening: Removal of halftone dot patterns during or after scanning printed matter by defocusing the image.
This avoids moire patterning and color shifts during subsequent halftone reprinting.
Deskew: Deskewing is the ability of the scanner driver to detect that the item being scanned is not straight.
When the deskew option is turned on the driver will attempt to straighten the image so that the resulting scan is level from left to right.
This feature is useful when attempting to OCR a document; however, it is important that when scanning from the flatbed the page be aligned to the alignment arrows.
When scanning from an ADF the input paper guides should be flush to the side of the pages being scanned.
Also See OCR ADF Scanner and Flatbed Scanner
Dichroic mirror: A special type of interference filter, which reflects a specific part of the spectrum, whilst transmitting the rest.
Used in scanners to split a beam of light into RGB components.
Digital: Method of data storage and / or transmission wherein each element of information is given a unique combination of numerical values ( bits ).
Each bit indicates either the presence or absence of a condition ( such as on-off, yes-no, true-false, open-closed ).
Digital data or voltages consists of discrete steps or levels, as opposed to continuously variable analog data.
Digital-to-Analog Conversion: ( D/A ) Conversion of digital information into a state of fluctuating voltage levels.
( DAC ) Interface to convert digital data ( represented in discrete, discontinuous form ) into analog data ( represented in continuous form ).
Digital Film: Quite simply that.
Solid state flash memory cards in place of emulsion film.
Digital Zoom: A digital magnification of the centre 50% of an image.
These give less than sharp images because the new zoomed image has been interpolated.
Don’t be swayed by the incredible 500% zooms on some cameras, the images won’t be really acceptable.
The optical zoom gives much more clarity to an image.
Digitisation: The process of converting analogue information into digital for use by a computer.
Dioptre Adjustment: This adjusts the optical viewfinder’s magnification factor to suit the eyesight of the cameras user.
There should be a knob or dial near the viewfinders eyepiece, however, not all cameras have this feature.
Direct-digital color proof: A proof made from a stored data file onto a substrate without producing intermediate separation film.
Display: A temporary visual representation of computer output on a CRT or other electronic device.
Dithering: The process of specifying color to adjacent pixels in order simulate a third color in a bitmapped image.
This technique is used when a full range of colors is not available.
Dmax: The highest level of density of a film positive or negative.
Dmin: The point of minimum density in an image or original.
DOF: Abbreviation of Depth of Field
Dot gain: A printing defect in which dots print larger than intended, causing darker colors or tones.
Dot gain measures the increase in halftone dot values that occur during the offset printing production process.
Total dot gain is measured as the difference in apparent dot size between the final printed product and the original film.
Dot gain occurs as the result of both mechanical and optical influences on the original dot size.
Download: Term used for the transference of image data from the camera to your computer.
Can be done via a serial port or the faster USB port.
Downloads can also be done via Bluetooth or Infra-red without the need for cables.
Down-sampling: The reduction in resolution of an image, necessitating a loss in detail.
DPI: Dots per Inch. This is a measurement value used to describe the resolution of a display screen or that of a printer.
A method of denoting the resolution of a scanned image, a digitized image in a file, or an image as rendered by an output device.
Also, used interchangeably with Pixels per inch ( PPI ).
DRAM: Dynamic Random Access Memory. A type of volatile memory, which is lost when the power is turned off.
DRAM Buffer: All digicams have a certain amount of fixed memory to facilitate image processing before the finished picture is saved to the flash memory card.
Cameras with burst more have a larger buffer of 32 MB or bigger to cope with the files however, they are more expensive.
Drum scanner: An optical input device that mounts reflective or transparent input media on a revolving cylinder for digitizing.
DSLR: Digital Single Lens Reflex ( SLR ). Camera with interchangeable lens.
DVD: Digital Versatile Disk. DVD is DVD recorded on a DVD-R or DVD-RW disc.
Dye Sub: Dye sublimination is a printing process where the colour dyes are thermally transferred to the printing media.
The printers use CMYK colour format.
The paper is run in and out of the printer 4 times, once for each colour ( C, M and Y ) and a fourth time when a protective overcoat is applied.
Dye sub is continuous tone printing, it prints tiny square dots each of which is denser in the centre and lighter on the edges.
The dyes are transparent so different coloured dots can be printed on top of each other to form any one of 16 million colours.
Dynamic Range: This is a measurement of the accuracy of an image in colour or grey level.
More bits of dynamic range results in much finer gradations being preserved.
Elliptical dot: A type of halftone screen dot with an elliptical rather than circular shape, which sometimes produces better tonal gradations. Emulsion: The coating of light-sensitive material on a piece of film. Emulsion down: This specifies a readable film image with the emulsion side facing away from the viewer. The printer usually decides whether emulsion should be up or down.
EPP: Enhanced Parallel Port. This is the newer, hi-speed, bidirectional printer port on modern PC’s.
EPS: ( Encapsulated PostScript ) This format carries a Pict preview and is the only format that supports saving line screen data and transfer functions.
In bitmapped mode, it also supports transparent whites.
Also see Pict
E-TTL: Canon’s “Evaluative Through The Lens” exposure system that uses a brief pre-flash before the main flash in order to calculate the correct exposure.
EV: Exposure Value. The ability to override the auto exposure system to under or over expose the image.
EXIF: Exchangeable Image File Format. The embedded information about camera and exposure for each image.
Most decent graphics programs can read this information.
Export: To output data in a form that another program can read.
Exposure: Amount of light that hits the image sensor of film controlled by the shutter speed and aperture.
Exposure Bracketing: Camera will take 3 or 5 images and varies the exposure up or down for each photograph ensuring at least one will be well exposed.
Exposure Compensation: You can lighten or darken the image by under or over exposing the image. ( EV compensation ).
F-Stop: Number indicating the size of the aperture.
It is an inversely proportionate number as in F-2.8 is a large opening and F-22 is a small opening.
File: A named collection of information stored as an apparent unit on a secondary storage medium such as a disk drive.
A collection of information like data, text or images which are saved on a CD. DVD or hard drive.
File Format: Type of program or data file.
Includes JPEG, TIFF and BMP
73 ICONS depicting Various File Formats
Fill in Flash: See Fill in Flash
Film: Photosensitive material, generally on a transparent base, which will receive character images, and may be chemically processed to expose those images.
Film negative: A piece of film with a reversed image, in which dark areas appear white, and vice versa. Film recorder: Used in reference to color transparency recording devices, and sometimes also to imagesetters.
FireWire: Officially known as the IEEE 1394 protocol. A high speed data transfer interface used on digital camcorders and the more expensive Digital SLR’s.
The IEEE 1394 interface is a serial bus interface standard for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple, who called it FireWire. The 1394 interface is comparable to USB though USB has more market share. Apple first included FireWire in some of its 1999 models, and most Apple computers since the year 2000 have included FireWire ports, though, as of 2014[update], it only remains as an interface on the Mac Mini-model, being replaced by the Thunderbolt-interface on all other Mac-models. The interface is also known by the brand i.LINK (Sony), and Lynx (Texas Instruments). IEEE 1394 replaced parallel SCSI in many applications, because of lower implementation costs and a simplified, more adaptable cabling system. The 1394 standard also defines a backplane interface, though this is not as widely used. IEEE 1394 is the High-Definition Audio-Video Network Alliance ( HANA ) standard connection interface for A / V ( audio / visual ) component communication and control. FireWire is also available in wireless, fiber optic, and coaxial versions using the isochronous protocols
Firmware: A micro program often used and stored in ROM.
Normally the ROM based software is in all computer based products from PC’s to digital cameras.
You will often see firmware updates for electronic goods that deal with problem issues.
Fixed Aperture: Aperture remains constant regardless of the lens’ focal length. I.e.
The Canon “L” series have a constant fixed aperture when zooming.
Fixed Focal Length: Basically a non zoom lens. 100mm, 50mm, 200mm etc.
Flash Memory: This is the equivalent to film for digital cameras.
It can be re-used over and over and some of the better brands have a lifetime warranty.
Types include Compact Flash (CF), Smartmedia, memory stick etc.
Flat Bed Scanner: Optical Scanner in which the original image remains stationary while the CCD sensors pass over or under it.
The scanned image is held flat by the lid hence the name.
Any scanning device that incorporates a flat transparent plate, on which original images are placed for scanning.
The scanning process is linear rather than rotational.
Focal Length: A lens’ angle of view.
Such as Wide angle, standard or telephoto.
Focus Assist: Cameras with this send out a light, either normal or infra red to light up the subject to assist with the autofocus in low light or darkness.
Focus Lock: Focus lock means pre-focussing the subject and re-framing by moving the camera.
This is done by half pressing the shutter to focus and fully pressing to expose.
Done to ensure crisp, sharp eyes for example.
Frame: One of many still pictures that make up a video.
Frame-grabbing system: A combination of hardware and software, designed to capture individual frames from video clips for further digital manipulation, or consecutive replay on computer platforms.
Frame Rate: Number of frames that are shown or sent each second.
Live action is around 30 frames per second.
Gamma: Measure of the amount of contrast in an image according to the properties of a gradation curve.
High contrast = High Gamma and Low = Low.
A mathematical function used to describe the relationship between input densities ( levels ) and output densities ( levels ).
The measure of how compressed or expanded dark or light shades become in an image.
Gamma Correction: With reference to displaying an image accurately on a computer screen, Gamma correction controls the overall brightness of an image.
Images which are not properly corrected can look either too dark or bleached out.
The correction of tonal ranges in an image, normally by the adjustment of tone curves.
Gamut: This is the range of colours that are available in an image or output process.
Gamut is generally used in describing the capabilities of a printer to reproduce colours accurately and vibrantly.
The limited range of colors provided by a specific input device, output device, or pigment set.
Gang scanning: Sequential scanning of multiple originals using the same previously-defined exposure setting for each.
GIF: A graphic file format mainly used for Web graphic or small animated Graphics Interchange Format - GIF files.