File Formats

1
File Formats
GIF graphical interchange format JPEG joint
photographic experts group PNG portable network
graphics TIF tag image file format BMP
windows bitmap PCX windows paint brush PICT
Macintosh Quickdraw
2
GIF Files

• GIF files are cross platform
• GIF files are compressed
• GIF images use indexed color or a max of 256
  colors
• GIF files are interlaced.
• GIF files are best used for web pages.
• GIF files are best for images with large areas of
  solid color (for example, logos, text as
  graphics, cartoons).

3
JPEG Files

• JPEG files are cross platform
• JPEG files compressed but the compression scheme
  is loosy which means data is removed from the
  image to make it smaller.
• JPEG files are not interlaced must wait for
  image to download.
• JPEG files can contain 16.7 million colors
  (called 24 bit).
• JPEG files are best for photographs, watercolor,
  or any image with subtle transitions between
  colors.

4
PNG files

• PNG files are new and were developed after a
  CompuServe legal battle for royalty fees for GIF
  files.
• PNG files are cross-platform and compressed.
• PNG files use a lossless compression scheme
  no data loss and then can compress smaller than a
  GIF.
• PNG files can be either 256 color or 16.7 million
  true colors.
• PNG files include gamma information or
  brightness
• PNG files will eventually replace GIF files as
  soon as all browsers are updated to read them.

5
TIF File

• TIF files were developed by Adobe and is the most
  widely supported.
• TIF files are large files and it uses lossless
  compression.
• TIF files are too large to email.
• TIF files are used for print material.

6
BMP, PCX PICT Files

• BMP is lossless and TIF PNG. BMP will handle
  24 bit data but it cannot be compressed.
• PCX (Windows PaintBrush) is lossless like TIF and
  PNG
• BMP PCX files are not universally used except
  in Windows and their compression is low.
• PICT (Macintosh Quickdraw) is lossless like TIF
  and PING but cannot be read by Windows.

7
Color

• CMYK Color
• Cyan (blue) Magenta (red) Yellow and Black
• This is a full color printed piece which
  designers call a four color process.
• The image is created by layers of dots. Green
  would be created by a value of cyan printed on
  value of yellow.
• CMYK is a reflective color model. The light
  hits the color and reflects back to the eye.

8
Indexed Color
Indexed color is used for web graphics Indexed
color mode is simply a limited selection of color
called a palette of up to 256 colors. When you
convert a image to GIF it will change it into an
indexed color image and delete all but 256 RGB
colors limited to the palette. In PhotoShop you
can choose the palette you wish to use. You can
also reduce the palette make the file even
smaller.
9
RGB Color
RGB stands for Red, Green Blue. Monitors,
including television, video and computers, all
create images on the screen by emitting red,
green and blue light. It is not reflective. RGB
values are created and the combination of these
values produce various colors (eg. R25, G178,
B115 produce green). Many graphics software will
allow you to enter RGB values to create the color
you want. Every image you create for a web page
should be saved in RGB mode.
10
DPI vs. LIP vs. PPI
DPI Dots per inch units used to measure the
resolution of a printer LPI Lines per inch
The offset printing 'lines' or dots per inch in a
halftone or line screen. PPI Pixels per inch
the number of pixels per inch in screen/scanner
file terms.
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Scan for Output
72 dpi web 150 dpi laser printer/DeskJet
printer 300 dpi tonal art for offset
printing 800 dpi line art output for offset
printing
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Printer Myth
Even though your printer will say it print 600
dpi or higher, this is really untrue. This
information is referring to image resolution not
printing. Most LaserJet/DeskJet printers only
print at 80 little dots per inch. Always scan
dpi screen ruling (lpi) x 2
13
Talk to the Print Shop
Before scanning photos for brochures, talk to
your printer. Find out what screen resolution or
dpi is required. Ask what file format they
need. Then scan at twice the dpi or resolution
they need and save in correct file format.
14
Remember!!
Always scan your images at the size you will be
using them in the final layout, or larger. The
the scale percentage in Scan Wizard to change
scan size. If you are not sure of the output,
save the file in PhotoShop as a .psd.
Interesting note, every time you open a JPEG
file and then save it again, the color degrades.