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Dictionary |
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| Bit |
A bit is the smallest element of digital information.
A bit can hold "2" values. Its value is either "1"
or "0". |
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| Byte |
A byte is 8 bits. Each byte can represent values
0 to 255. (2x2x2x2x2x2x2x2=256) |
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| Compressed |
When you save a photo to disk as a JPEG file, it
is "compressed" or made smaller to save space. You can
see the compressed file size by opening the folder that the file
is in, and highlighting the file. The size will be displayed in
the window's status bar. (Or right click on the file and look at
its Properties.) See "uncompressed" also. |
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| DPI |
DPI stands for Dots Per Inch. DPI is the amount of
dots per inch a printer makes when it is printing a file or photo. |
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| FTP |
FTP stands for File Transfer Protocol. A set of standards
used to transfer files. An FTP site is a server (or computer) on
the internet that is used to store files. You can upload to (or
download from) the FTP site using an FTP program. |
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| Grayscale |
A photo with no color. Uses one byte per pixel. Each
pixel can display 256 levels of brightness. 0 is Black and 255 is
White. Everything in between is the shades of gray that make up
the photo. |
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| Gamma or Monitor Gamma |
CRT's (or monitors) do not produce a brightness that
is proportional to the input voltage. Instead, the brightness produced
by a CRT is proportional to the input voltage raised to a power.
This power is a variable (or number) called gamma.
Output Luminance = Signal ^ Gamma
The value of gamma varies depending on the CRT. Values are usually
between 1.4 and 3.0. Macs are usually around 1.8 and PC's are
around 2.2.
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| Highlights |
The levels in a photo that are toward the higher
end of the 0 to 255 value range. Pixel values near the white point
255. |
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| Histogram |
A graph that represents the brightness levels in
your photo. Its X axis goes from 0 (black) to 255 (white). The Y
axis represents the number of pixels at each of those values. |
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| JPEG File |
A compact photo or graphics file (see compressed).
When uploading for services, save your photo in this format. After
scanning your photo, save to your disk as a jpeg file (myFile.jpg).
Save at the "High" or "Maximum" quality setting. |
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| KB |
Stands for kilobyte or 1000 bytes. 500KB is five
hundred thousand bytes. Files in this size range are usually for
viewing on a monitor only, or for making very small prints (smaller
than wallet size). Pixelation will occur if printed at larger sizes. |
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| Levels |
The brightness values of the pixels that make up
a digital photo, ranging in values from 0 to 255. Each pixel in
a photo will have a level (or value) assigned to it. In a color
(RGB) photo each pixel will have a level for red, a level for green
and a level for blue. Grayscale photos only have one black level
(or value) for each pixel. |
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| MB |
Stands for megabytes or 1,000,000 bytes.
5MB is 5 million bytes. |
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| Midtones |
The levels in a photo that are around the middle
of the 0 to 255 value range. (The tones or pixels that has byte
values around 128.) Anytime you change the midtones of a file in
an imaging program , it will destroy some of the levels (same goes
for changing black and white points). It's best to adjust the levels
only one time. |
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| Pixel |
Pixels are the tiny squares that make up a digital
photo. You can see the pixels if you zoom in all the way into a
digital photo using your imaging program. |
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| Pixelation |
Pixelation is when you can see the pixels in a photo.
Occurs when you try to enlarge from a file that is too small. |
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| PPI |
Stands for Pixels Per Inch. PPI is the amount of
pixels per inch (in the file) used to make up the image. |
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| Resolution |
The amount of PPI of a photo file, or the amount
of DPI that a printer prints. |
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| RGB |
Stands for Red Green Blue. Your monitor uses a mixture
of these colors to display 16 million colors. Each pixel in a RGB
image uses the values of the Red byte (8 bits), the Green byte (8
bits) and the Blue byte (8 bits) to determine the displayed color.
That's 24 bits per pixel (or 3 bytes per pixel) to determine each
pixel's color. Each color (Red , Green and Blue) can have one of
256 levels of brightness making up the possibility of "16 million
colors " . (256x256x256=16,777,216). The combination of the
brightness from each color (RGB) makes the "perceived"
color you see. |
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| Shadows |
The levels in a photo that are toward the lower end
of the 0 to 255 value range. Pixel values near the black point 0. |
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| True color |
True color (24 bit) means displaying a photo in 16
million possible colors. Select this setting (True Color, 24 bit,
or 16 million colors) for your display when working with digital
photos. |
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| Uncompressed |
When you open a file in your imaging program it is
uncompressed to is full size. When you scan a file into your computer
it is uncompressed while it is open in the your imaging program.
The program will show the uncompressed size (usually on the status
bar). See "compressed" also. |
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| White Point & Black Point |
Pure white is at level 255 (white point). Pure black
is at level 0 (black point). Anytime you change the black or white
points of a file in an imaging program, it will destroy some of
the levels (same goes for adjusting the midtones). It's best to
adjust the levels only one time. |
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