VECTOR, RASTER, DPI, LPI, TRAPPING …
WHAT DO THESE TERMS MEAN?

Confused by all the technical mumbo-jumbo? Here’s a quick guide to understanding the terms.

• What is Vector art?
• Why does my art have to be in Vector format?
• Can a bitmap image be converted into Vector art?
• Why do I have to convert fonts to outlines, and how do I do that?
• What do DPI, LPI, and PPI mean?
• What if my art doesn’t meet your specifications?
• If I don’t have an illustration program, how do I create my art?
• Why can’t I submit Microsoft Word or Publisher files?
• Have a question that isn't listed here? Contact us!

WHAT IS VECTOR ART?

Vector images are shapes and lines drawn in an illustration program (like Adobe Illustrator or CorelDraw) that have mathematical dimensions. This allows unlimited scalability without compromising the image quality. Images have smooth edges at all sizes, and file sizes much smaller than bitmap images. Common vector formats are Adobe Illustrator (AI), Encapsulated PostScript (EPS), and Corel Draw (CDR). TrueType, Open Type, and PostScript Font files are also vector files.

Bitmap images are made up of a series of individually defined pixels and have a fixed resolution. A 1” x 1” bitmap, at 300dpi, is 300 pixels wide and 300 high. Bitmap images CAN'T be scaled without losing quality. For printing, the higher the resolution of bitmap files, the better the image quality. Common bitmap formats are TIFF, JPG, GIF, PNG, BMP.

WHY DOES MY ART HAVE TO BE IN VECTOR FORMAT?

Vector art provides much cleaner and smoother lines and edges to the art. Any half-toning on plastic bags is printed at no smaller than 35 lpi, which can result in jagged or uneven edges if using a bitmapped image.

CAN A BITMAP IMAGE BE CONVERTED TO VECTOR ART?

Yes, but not always easily. Depending on the complexity of the image, converting bitmaps to vector art can be simple or very time consuming. Usually, converting bitmaps to vector art requires "rebuilding" the art from scratch – matching fonts, and redrawing lines. Some art can be automatically traced by illustration programs, but the results vary depending on the design. Placing a bitmap into an illustration program and saving as an EPS or PDF does NOT convert the file.

WHY DO I HAVE TO “CONVERT FONTS TO OUTLINES” AND HOW DO I DO THAT?

A font is a collection of letters, or glyphs, defined in a specific typeface. Each letter has a description of the shape, and how that shape should be displayed. Fonts can only be displayed on computers where the font file is installed. If the computer opening the document doesn’t have the proper font installed, programs usually substitute another font. Obviously, this can cause problems. Letters in fonts are made up of lines and shapes, and as long as they are confined to a font format, they will behave as fonts. Converting them to plain outlines disconnects the font descriptions from the letters, and keeps the shape from changing. Once the type is converted to outlines, it can no longer be edited as type.

To convert type to outlines, an illustration program like Adobe Illustrator or CorelDraw is required. Adobe InDesign is also capable of converting type to outlines. In Illustrator, chose “create outlines” from the Type menu. In CorelDraw, select “Convert to Curves” from the Arrange menu. In InDesign, chose “create outlines” from the Type menu.

PDF files use embedded fonts, and will print and display correctly, but if these files need to be edited, the computer opening the file must have the correct font, or it won’t display properly. It is best to convert fonts to outlines before creating a PDF file.

WHAT DO DPI, LPI AND PPI MEAN?

Both digital bitmap images and printed images are made up of a series of dots.

• DPI – Dots Per Inch –the resolution of a printed image, how many dots of ink printed per inch.
• PPI – Pixels Per Inch – refers to the number of pixels per inch (vertically and horizontally) in a digital image
• LPI – Lines Per Inch – refers to the lines of dots in a halftone or screen - the higher the number, the smaller the dots.

Printer DPI is generally a higher number than the image PPI, and the PPI is a higher number than the LPI. For most commercial printing applications, digital images need to be a minimum of 300 PPI. If there are image areas that will be halftoned (not a solid color), the LPI indicates the number of lines of dots per inch. For many print applications, LPI is approximately half the number of the PPI. For the process that we use for plastic bags, 35 is the maximum LPI that prints well.

WHAT IF MY ART DOESN’T MEET YOUR SPECIFICATIONS?

When your art comes in, it is inspected to make sure it is acceptable. If for any reason the art won’t print well, you will be contacted with information about the problem. Common issues involve embedded fonts, incorrect trapping, thin outlines, too much halftoning, and low resolution bitmaps. If you are unable to correct the issues, an art quote will be provided.

I DON’T HAVE AN ILLUSTRATION PROGRAM, HOW DO I CREATE MY ART?

If unable to create your art in an illustration program, you will probably need to hire a graphic designer to do the work for you. If you would like us to prepare the art, let us know and we will give you a quote.

WHY CAN’T I SUBMIT MICROSOFT WORD OR PUBLISHER FILES?

These programs, while powerful, are not designed for creating artwork for commercial presses.