Glossary of Terms
Bitmap is a type of graphical file format that represents images as a set of dots (called 'pixels'). Some formats also include compression to reduce file sizes. Bitmap formats are commonly used for photographs and grayscale images. Changing the size of bitmap images can result in changes to the image.
CMYK stands for Cyan Magenta Yellow Black, the colors used in the printing process. (K is used to avoid confusion with blue.) All files that were created in RGB color must be converted to CMYK before publication.
Compression is the process of squeezing data into smaller files to save disk space and/or download time. GIF and JPEG are file formats that use compression. A variety of techniques are used for compression, which normally rely on substituting or removing repeating strings of data. Utilities for file compression include Stuffit for the Macintosh and WinZip for Windows PCs.
DPI stands for dots per inch. DPI specifies the resolution of an output device, such as a computer screen or a printer, or an input device such as a scanner.
EPS stands for encapsulated postscript, a file format that uses mathematical equations (called a vector approach) rather than dots (as in a bitmap) to describe images. EPS is a subset of Postscript with some structural conventions. This format is useful for printing fine detail and allows scaling of images to any size without loss of quality. Unlike postscript, an EPS file often contains a preview of the image that will allow it to be viewed in a page-layout program. Generally, an EPS file can only be edited by the software program that created it.
Export means to save a file in a different format. For example, many Adobe Photoshop files can be exported to become GIF or JPEG files.
File format is a set of instructions that tell the computer how to store, access or transmit digital information. File compatibility requires being able to match the format of data created in one program to a format that can be opened by another.
GIF stands for Graphic Interchange Format. Files cannot be submitted in this format because its resolution is not adequate for print production.
Grayscale refers to images composed of 256 different shades of gray.
Half-tone is the 'breaking up' of images into dots so that they can be printed by the four-color process (CMYK). The effect can be clearly seen when you look closely at a large billboard poster.
Hard copy refers to high-quality images that can be scanned for printing in case the electronic figures are not acceptable. Note that hard copy printouts must be on glossy paper to scan properly. Hard copy does not refer to CD-ROMs, floppy disks or computer hard drives.
JPEG stands for Joint Photographic Experts Group, who wanted smaller files to transmit electronically. Because the format includes compression, files lose information each time they are saved as a JPEG, so it is advisable to save a file as a JPEG only once.
Layering is a feature found in many graphics programs, such as Adobe Photoshop. It allows parts of an image (including text) to be created and moved independently. It is similar in concept to overhead projector sheets placed on top of each other. They can be combined (flattened) to produce a one-layer image, or the layers can be kept intact so that they can be edited later.
Line art is any image that requires sharp edges and high contrast between areas of the image that have ink and areas that do not. These images require a high resolution to create the necessary sharpness, so they should generally be in Postscript or EPS format.
PICT is another type of bitmap format. PICT has been around since the early days of the Apple Macintosh and does not contain the complex information needed for print production. Thus we do not accept figures in PICT format.
Postscript is a page description programming language created by Adobe that is an industry standard for document and graphics output. The key feature of Postscript is device independence, which allows different output devices from different manufacturers, which may not be compatible through any other means, to print the same file in more or less the same way.
Resolution is the number of dots within a given area, usually (square) inches. This measure of image quality only applies to bitmap images. Low resolution can cause a jagged appearance to lines and contours. Generally a file that is 72 dots per inch (DPI, same as pixels per inch) will be suitable for viewing on screen, but will appear fuzzy when printed out. A file at 150 DPI will be ideal for printing on a desktop printer, and a file at 300-600 DPI will be suitable for professional printing. When you upload your files, our system converts them to PDF. We optimize the resolution for screen and desktop printer use, as needed for the review process. We also keep your original files in case higher-resolution images are requested. We do not routinely use high-resolution files during the review process because these can take a long time to download from the internet. If you are using Adobe Photoshop, the image resolution can be found in the 'Image Size' dialogue box under the 'Image' menu.
RGB stands for red, green and blue, the colors used to make up computer displays. RGB color often looks different from CMYK color. Although figures created and saved in RGB may look good on your monitor, they cannot be used for the journal's printing process. All figures submitted in color must be in CMYK. You can convert between RGB and CMYK in many software packages. Please be aware that the colors may look different after conversion and so may need to be adjusted.
RTF stands for rich text format, a generic word processing format that carries information about formatting and text. It keeps a record of bold or italic text, the font used and paragraph indents. A file saved in RTF from Word Perfect will translate to Word and retain most of its formatting.
TIFF or TIF stands for Tagged Image File Format. This bitmap format is the most commonly used in professional printing. It is versatile and can contain color information as grayscale, RGB or CMYK. Built-in compression techniques allow these files to take up relatively little disk space.
Vector is a type of graphic image drawn in shapes and lines, called paths. Images created in Illustrator and Freehand (graphic design software) are vector graphics. The advantage of this format is that artwork can be scaled and manipulated without loss of quality. Vector graphics are resolution independent, that is, they will print up to the capabilities of the output device without any loss of quality. EPS is a vector format.