Transcript Photoshop Basic Theory

Photoshop
Basic Theory
Bitmap vs Vector
Bitmap based on pixels
Pixel is the smallest element of a bitmap
 Used in Photoshop
 Change in size changes quality
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Vector based on mathematical formula
Used in Illustrator
 Change in size does not affect quality
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Bitmap
Measured in pixels
Bit-depth is the amount of digital
storage space used to record
information about the color of a pixel
24 bit scan with 256 gray levels
24 bit monitor with 16 million colors
Pixel
Short for picture element
Smallest element of a bitmap
In Photoshop you edit pixel information
Change color
 Change shade
 Change brightness
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Resolution
Measured in pixels per inch (ppi)
Pixel size varies based on resolution
100 ppi : 1 pixel = 1/100 of an inch square
 300 ppi : 1 pixel = 1/300 of an inch square
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Dragging a corner and changing size
does not change the number of pixels
Printer resolution is not the same as
image resolution
Color Models
RGB – Red Green Blue
Mirrors the way a human eye sees color
 Used in scanners, digital cameras, and
monitors
 RGB are the “additive primaries”
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100% of Red Green Blue light = White
Color Models
CYMK – Cyan Yellow Magenta Black
Used in Printing
 CYM are secondary colors
 Also called the “subtractive” model
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Take away all 3 when printing = white
 All 3 together should make black but makes a
muddy brown because of impurities
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Printers add Black to make a true black
Color Gamut
The range of colors that a specific
device is capable of producing
Makes the printing process complicated
Gamut of a monitor does not equal the
gamut of a printer.
 Some colors can’t be matched
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Vibrant yellows or deep blues
Which Mode to Use
Use RGB mode if image is intended for
WWW.
Use CYMK or RGB if image is intended
for print but make sure you convert to
CYMK before going to another program
to set up printing (Illlustrator)
Color management
Several settings available in Photoshop
Edit Menu >>Color Settings
Use Web Graphics Defaults for WWW
Use US Prepress Defaults for print
Can create custom but not
recommended for amateurs!
Monitor Calibration