PPB October 2015

cups, which typically require a one- or

two-color imprint. While a vector file is

usually used for minimal color art, it can

accommodate many colors including

gradients and tints or shades of colors.

Raster artwork, on the other hand, is

tonal artwork created by series of small

dots or pixels. Photographs or painted

illustrations would be examples of this

type of art. Unlike vector images, individ-

ual shapes can’t be selected in raster art.

Raster artwork loses its sharpness when

enlarged, becoming increasingly blurry

and pixelated. When creating this style

of artwork it’s important to know the

largest size needed to produce a prod-

uct. Raster artwork that’s created at its

actual size can be reduced if necessary

for other applications. This type of art-

work is becoming more popular with the

growth of digital printing.

File Resolution

Another component to be aware of when

setting up a raster design is the resolution.

For a full-size t-shirt design, a resolution

set at 300 dpi is ideal. When creating a

design for screen printing, the general rule

is to set the resolution at 1 ½ to two times

the halftone screen that will be used to

print the image. So, if the printer will be

using a 45-lpi line screen, the image could

be saved at a resolution of 90. However, it

is not recommended to set a resolution

below 150 dpi. For large format graphics,

sometimes a lower resolution such as 150

or 200 dpi can be used. It’s always best to

check with the printer to learn what sizing

and resolution they require.

Vector Vs. Raster:

Which To Use?

While vector artwork is an option for

digital printing and screen printing, it is

required for cut-vinyl decorating. The

cutter reads the nodes and paths that

are created in the vector file in order to

know where to cut. A raster image that’s

used for print-cut artwork will need to

be saved and placed in a vector pro-

gram such as Adobe Illustrator or Corel

Draw in order to create the vector out-

line cut path.

Vector files are also used by embroi-

derers when digitizing a design to be

sewn. The vector layout is created and

then imported into digitizing software.

The embroiderer then selects the shapes

and applies the appropriate stitch.

Rhinestone templates are made using

vector files. The templates are created by

laying out appropriate-sized circles in the

preferred design shape. The holes can

then be cut out to create a template for

the placement of the rhinestones.

Vector artwork isn’t normally recom-

mended for digital processes because

with large areas of solid color, if a print

head gets clogged, streaking or banding

can become more evident. On the other

hand, vector artwork is a good choice for

screen printing because it results in

smooth coverage of large solid areas

without streaking.

Raster artwork is perfect for all types

of digital printing as well as screen print-

ing. However, creating separations for a

raster design is much more involved and

requires more colors and screens, so it

can be more costly. For digital printing,

the nature of the full-color raster image

helps camouflage any streaking that may

occur if a print head becomes clogged.

File Formats

Regardless of whether you create a

raster or a vector image, there are

numerous file formats out there, and

each process and even production

device requires its own specific file for-

mat in order to produce the job correctly.

Vector file formats include ai (Adobe

Illustrator), cdr (CorelDraw), pdf (Portable

Document Format), and eps

(Encapsulated Postscript). While ai and

cdr files are native to those programs, ai

files are recognized industry-wide and

can be recognized by other software and

production equipment.

Both eps and pdf formatted files can

be saved out of vector and raster pro-

grams. When saved out of a vector pro-

gram such as Illustrator or Corel Draw,

the file will retain its vector characteris-

62 •

PPB

• OCTOBER 2015

GROW

THE ABCs OF GARMENT DECORATING

When creating a design for screen printing,

the general rule is to set the resolution at

1 ½ to two times the halftone screen that

will be used to print the image.