Basic File Formats

There are two basic file formats for graphic images: Vector files and
Bitmap files. The next few pages will cover some of the major differences
between vector and bitmap files, as well as the advantages, disadvantages
and other issues that need to be considered when creating files for graphic
production.

Vector Graphics (lines):

These images consist of lines and curves that are defined by mathematical
objects called vectors. Vector art is created by combining various
geometric shapes, such as circles, triangles, or squares. In the diagram of
the key, you can see all of the separate shapes that have been combined
to create the entire image. Each of these shapes is an individual element
that can be manipulated or scaled by itself or in conjunction with all others
without any loss of quality.

Bitmap or Raster Graphics (images):

These images consist of colored squares, also called pixels. Bitmap
images are created by combining a series of various colored pixels. The
best analogy for a bitmap image is a child's toy called a LiteBrite. This is a
board with a light behind it to show an image created by inserting
translucent colored pegs. These pegs would be equivalent to a pixel in a
bitmap image. The more pegs, or pixels in one inch of a row, the better the
final image will look. If an image is created with enough pixels per inch, the
eye loses its ability to see the individual pixels.
Although vector and bitmap images are very different and have distinct
advantages and disadvantages, neither format is better than the other.
Which format you decide to use to create your graphics largely depends on
the final result you are looking for. Many times you will use a combination
of both file types.

Traditional graphics:

Vector art is the ideal file format for creating files for
traditional graphics. The process used to create traditional graphics
requires that every image be outlined so that the vinyl cutter can cut the
various pieces. With a vector art file, this is extremely easy to do.

Digital graphics:

Vector images also work great for digital graphics as long
as the desired result is not a photo-realistic image.

Color Issues:

The colors in a vector file can be changed or adjusted relatively easily.
Either the entire image or just a portion of the image can be manipulated.

Vector Software:
Adobe Illustrator (drawing program)
Adobe InDesign (layout program)
Freehand (drawing program)
Quark Xpress (layout program)

Advantages:
• Images can be enlarged to any size without sacrificing quality. Because
the art is resolution independent, meaning that there are no dots being
used to create the image, there is nothing to limit its enlargement
capabilities. Images can be reproduced at any size while maintaining crisp
outlines and details. This makes them the ideal choice for type and other
bold graphics, such as logos, which require clean lines that can be scaled
to any size.

• Vectors are very compact information files, which means that the file
sizes are typically going to be very small. This makes for easy and fast file
transportation via modem or floppy disk. A vector file set up for a 4-panel
mural may average 30-500 Kilobytes, whereas the same image created in
a bitmap file can be 250-400 Megabytes - an increase of over 80,000%!

• Vector images can be manipulated very easily because each piece of the
image is a separate/individual entity. This makes moving or resizing a
portion of the image or the entire image itself very easy. Adding to and
deleting from a vector image is also fairly simple to do.

Disadvantages:

• The biggest drawback to consider when working with vector graphics is
that creating a complicated or photo-realistic image is very difficult and
time consuming to do.

• When a photo is placed into a Vector program, it increases the size of the
file. The Graphics Department recommends using F.P.O. files within
Vector programs and send large photos separate.

Bitmap or Raster Images Uses:

Traditional graphics:
Bitmap images are great for digital printing. They have the ability to
produce both very detailed and photo-realistic or very simple images.

Digital graphics:
Bitmap images can only be used for traditional graphic production if they
are converted into a vector art file. To do this, the file is sent through a
program that attempts to trace the lines it sees in the bitmap file. This will
only work with simple images and still often requires clean-up, especially
when type is present.

Color Issues:
• CMYK or RGB files are acceptable. The Graphics Department will make
sure and convert the images into the correct color space for the specific
output devices. Keep in mind that using one of the generic color spaces
provided on all PC and MAC computers will ensure accurate color
conversion. The recommended color spaces are RGB S, color match
RGB.ICC or PhotoShop 5 CMYK defaults.

• Adjusting the color of a bitmap image can be very difficult to do. In most
cases, the color of one object cannot be adjusted without shifting the color
of the entire image without extensive work to isolated areas and feathered
selections.

Raster Software
Adobe Photoshop
Scanning pre-existing artwork and photos

Advantages:

• Accurate photo color management in PhotoShop.

• Vectors are very compact information files, which means that the file
sizes are typically going to be very small. This makes for easy and fast file
transportation via modem or floppy disk. A vector file set up for a 4-panel
mural may average 30-500 KB, whereas the same image created in a
bitmap file can be 250-400 MB.

• Preexisting artwork can be scanned (photos, slides, original artwork) to
create a bitmap image. These can be produced either by themselves or
combined to create a collage - depending on the desired result. Reliability -
what you see at 100% is what you get.

Disadvantages:

• Manipulating a bitmap image can be very difficult to do. Although there
are potentially thousands of individual pixels in each inch of the graphic,
they all combine to form one single image. Isolating an individual pixel from
all of the others is virtually impossible to do. This makes changing the
layout, or removing from or adding to the image, a very time consuming
and potentially difficult task. The more detailed and intricate an image is,
the harder it is to do any kind of manipulation. Any changes that are made
may be obvious if they are not done correctly.

• The file sizes of bitmap images can be very large, especially for mural
panels and other large graphics. Information must be stored for every pixel
in the image, which means that the larger the image is, the more
information will be required from the scanner and the larger the file size will
be.

• Image enlargement is limited by the original size at which the file was
created. If a file is produced at a size that is larger than its resolution will
allow, the quality will decrease. Printing a low-resolution file will result in
pixilation - large pixels that produce very coarse-looking output. As
mentioned earlier, the eye eventually loses its ability to see the individual
pixels if the resolution is high enough. Conversely, when a small bitmap
image is enlarged, the pixels become more apparent to the eye. These
low-resolution images look "choppy" or "built from blocks."