Technical FAQ and Information
GIF and JPEG formats not good for print
Saving images for high-resolution printing and for the Web require very different procedures. One thing that is important is to use the correct file formats.
Use only TIFF and EPS file formats when creating images for print pieces. They work for everything from photographs edited in Adobe Photoshop to drawings made in Illustrator or Freehand. Except for some flavours of EPS, do not use other file formats for final output.
Two popular file formats for the Web have been known to creep into print production workflow and should be avoided.
GIF (Graphics Interchange Format) was developed by the online service provider CompuServe. Good for Web graphics, GIF format compresses the colour palette down to 256 colours or less. This makes the file smaller and decreases download time. GIF images are also suspect for having a low resolution of 72 dpi. This is acceptable for a monitor, but rarely for the printed page.
JPEG (Joint Photographic Experts Group) is good for compressing and archiving photos and is the dominant file format for photo-realistic images on the Web. Many photographers or scanner operators will JPEG their images for storage on CD or disk. These images then need to be reopened in an image-editing application (like Photoshop), edited and saved in an acceptable file format for print. Some other file formats that should not be used for photographs for print jobs include Windows Bitmap (BMP), AMIGA IFF, PlashPix, PCX, PICT, Pixar, PNG, RAW and Targa.
How can I tell what resolution the image from my digital camera is?
Some digital cameras will let you know what the image resolution is, while others will tell you what the pixel dimensions of your image are. If you know what the pixel dimensions of your images are either from the camera itself or through the image editing software, you can do a little math to determine the resolution, and the size you can print the image at for clear and crisp printing.
Pixels รท 300 = inches
Simply write down the pixel dimensions of your image and divide those numbers by 300. For example: An image has a pixel dimension of 600 x 900 pixels. Once each dimension is divided by 300 the result is 2 x 3 inches. This means that you can use this image at 2 x 3 inches or smaller in your layout for quality printing results.
If your image editing software does not tell you what the pixel dimensions are, but it does tell you what the resolution is, then you know the maximum size you can use that image in your layout. We recommend that images be at 300 dpi in their final size in the layout. Please keep in mind that resolution and physical dimensions are in direct proportion to each other. If you have an image that is 2 x 2 at 300 dpi (dots per inch), and increase its size in the layout to 4 x 4 the new resolution is 150 dpi (dots per inch). So remember, when you bring an image in to your layout you can shrink it down in size (because the resolution will increase) but you will be limited as to how far you can increase it in size.
JPEG IMAGE QUALITY: Digital cameras are geared primarily for consumer use. This means that default settings on many cameras go for quantity, not quality. The JPEG (.jpg) compression format is capable of completely ruining any image when compression is set too high. Always use the maximum quality settings on your camera when taking pictures for print.
RESOLUTION: Resolution is measured in dots-per-inch at the final reproduction size. THUS an image that measures 2 x 2 inches at 300 dpi contains exactly the same amount of information as an image that's sized at 6 x 6 inches at 100 dpi (dots per inch). Information -- like energy -- can't be created, but unlike energy, it can be destroyed by resizing.
LPI, DPI, oh my........
Defining a few common print acronyms
Acronyms are a part of life. So, they are also a part of the process of preparing files for printing. Here are a few defined.LPI or Lines Per Inch generally refers to the frequency of the halftone screen used in a printing job. For example, you may read in the back of an expensive art book that it was printed at "200lpi." Determining the lpi for a print job hinges on the paper used and on the print job. Many magazines are printed at 133lpi and newspapers are generally printed at around 85 lpi.
DPI stands for Dots Per Inch. It is used to measure resolution of an image, output device, scanner or monitor and can be a little confusing. In prepress file preparation, the most important use of DPI is in image resolution. For example, a 72-dpi image off the Web probably doesn't have enough dots to print out very nicely. But an image scanned at 300 dpi and placed in the document at 100% will work very well. It is far better to have too much resolution than too little, so leave a little extra in case you want to crop or resize an image. But don't go overboard because high-resolution images take up a ton of hard drive space and waste time printing and editing.EPS is a graphic format developed by Adobe Systems, Inc. It is a popular format to save your images for print. Short for Encapsulated PostScript, it is the preferred format for saving vector images made in Adobe Illustrator and Macromedia FreeHand. Many designers and prepress professionals only use the EPS format for saving their images.