Vector graphics are made up of lines and curves deﬁned by mathematical objects called vectors.
Vectors describe an image according to its geometric characteristics. For example, a bicycle tire
in a vector graphic is made up of a mathematical deﬁnition of a circle drawn with a certain
radius, set at a speciﬁc location, and ﬁlled with a speciﬁc color. You can move, resize, or change
the color of the tire without losing the quality of the graphic.
Vector graphics are resolution-independent—that is, they can be scaled to any size and printed at
any resolution without losing detail or clarity. As a result, vector graphics are the best choice for
representing bold graphics that must retain crisp lines when scaled to various sizcs—for
Bitmap imagesﬁtechnically called raster images—use a grid of colors known as pixels to
represent images. Each pixel is assigned a speciﬁc location and color value. For example, a
bicycle tire in a bitmap image is made up ofa mosaic of pixels in that location. When working
with bitmap images, you edit pixels rather than objects or shapes.
Bitmap images are the most common electronic medium for continuous-tone images, such as
photographs or digital paintings, because they can represent subtle gradations of shades and
color. Bitmap images are resolution-dependent~that is, they contain a ﬁxed number of pixels.
As a result, they can lose detail and appear jagged if they are scaled on-screen or if they are
printed at a lower resolution than they were created for.
The number of pixels displayed per unit of printed length in an image, usually measured in pixels
per inch (ppi, often referred to as dpi). In Photoshop, image resolution and pixel dimensions are
interdependent. The amount of detail in an image depends on its pixel dimensions, while the
image resolution controls how much space the pixels are printed over. For example, you can
modify an image’s resolution without changing the actual pixel data in the image—all you
change is the printed size of the image. However, if you want to maintain the same output
dimensions, changing the image’s resolution requires a change in the total number of pixels.
When printed, an image with a high resolution contains more, and therefore smaller, pixels than
an image with a low resolution. For example, a l-by-l-inch image with a resolution of 72 ppi
contains a total of5 184 pixels (72 pixels wide x 72 pixels high = 5184). The same l-by-l-inch
image with a resolution of 300 ppi contains a total of 90,000 pixels. Higher-resolution images
usually reproduce more detail and subtler color transitions than lower-resolution images.
However, increasing the resolution of a low-resolution image only spreads the original pixel
information across a greater number of pixels; it rarely improves image quality.
Using too low a resolution for a printed image results in pixelation—output with large, coarse-
looking pixels. Using too high a resolution (pixels smaller than the output device can produce)
increases the ﬁle size and slows the printing of the image; furthermore, the device will be unable
to reproduce the extra detail provided by the higher resolution image.
The CMYK model is based on the light-absorbing quality of ink printed on paper. As white light
strikes translucent inks, part of the spectrum is absorbed and part is reﬂected back to your eyes.
In theory, pure cyan (C), magenta (M), and yellow (Y) pigments should combine to absorb all
color and produce black. For this reason these colors are called subtractive colors. Because all
printing inks contain some impurities, these three inks actually produce a muddy brown and must
be combined with black (K) ink to produce a true black. (K is used instead of B to avoid
confusion with blue.) Combining these inks to reproduce color is called four-color process
printing. We recommend the CMYK model for all, full-color images.
Document Creation Guidelines
l. Document page dimensions should be the same as the publication’s final trim size.
2. Any element that is to extend to the trim edge of the publication should be extended l/8″ beyond trim for bleed.
3. No lines or anchored rules are thinner than .2 points.
4. All picture box frames have been specified correctly. If rule lines are for showing position only, indicate as FPO (for position only) on the laser to ensure that they will be deleted.
5. All images are positioned correctly in their picture boxes.
6. There are no gaps between images and borders or rules around the images.
7. You only have included fonts you intend to use, both screen and printer fonts. (Please do not send your completejont library.)
8. All unused colors should be deleted.
9. Colors should be deﬁned correctly in color palette. (PMS colors as spot, process builds as process separation, CMYK.)
10. The pasteboards surrounding all pages should be empty. This will reduce the ﬁnal size of the ﬁle.
11. When preparing a ﬁle, save as will reduce the ﬁle size. (This eliminates mini saves within the document.)
12. In Quark XPress only – grayscale / full color TlFFs are in picture boxes with a none ﬁll.
13. No files have JPEG compression applied.
14. All RGB files are converted to CMYK or grayscale.
15. Perfect bound should be set up in the page layout program on single page spreads. Full bleed backgrounds and elements should be extended to bleed off all 4 sides by at least 1/ 8″.
16. All documents should be laser proofed for typographical errors and correct separation of all elements. (Both composite and color separated lasers are helpful.)