16 Illustrations and artwork
16.3 Digital artwork and graphics files
The preferred method of handling illustrations for publication in all types of media is via digital artwork. This route has many benefits to the author and the publisher, and has clear advantages over using hard copy. By originating and manipulating artwork, the author has complete control over the final illustration and the production times/costs are minimized for the publisher.
It is very important that digital artwork is prepared in the correct format. Many publishers have their own specific guidelines for authors and general guides/resources are available on the web.
16.3.2 Files and file types
Graphics files can be bitmap (also known as raster) or vector based.
• Bitmap graphics consist of many small elements called pixels. Bitmap images are continuous tone images (see
16.4) produced when using a digital camera or scanning an existing illustration, or can be created and edited in raster graphics software.
• Vector graphics consist of separate mathematically described shapes called objects. Vector images are usually used for line artwork (see
16.4) and can be created using vector graphics software.
A final illustration may use a combination of vector and bitmap elements.
Graphics files are supported by many file formats. Standard image formats include:
common bitmap file format produced by most digital cameras; best used for continuous tone illustrations. JPEG is a lossy format, meaning that it discards colour information to produce a compressed file. This is not normally an issue for online publication, but may be noticeable in print.
The preferred bitmap format for continuous tone illustrations. TIFF files are significantly larger than JPEG files and can be either uncompressed or compressed using lossless compression. Unlike JPEG, TIFF files can support multiple layered images, where elements of the image exist in separate layers that can be manipulated without affecting the others.
standard format for vector (line artwork) graphics. Bitmaps can also be embedded in EPS files, making this a recommended format for combined vector/bitmapped illustrations. EPS files are high-quality, very large memory files because of their lossless format.
These exchange formats can be viewed using most software packages.
Application-specific formats such as PSD (bitmap) and AI (vector) are designed to be understood only by the software in which they were created (Adobe Photoshop and Illustrator, respectively); however, they can be easily converted to exchange formats.
PDF files are used for creating and digitally transferring documents, including text and graphics, in the final intended layout. These may be suitable for print, depending on the quality of any embedded images and the output options selected.
Word-processor, spreadsheet, and presentation files are not suitable for high-quality print output. GIF files, which can also support animated graphics, and PNG files are useful for simple web images, but not for print. BMP files offer no advantage over other formats and should be avoided. RAW files are produced by high-end digital cameras, and require processing and conversion to a standard format such as JPEG or TIFF.
16.3.3 Size and resolution
Supply digital artwork at the same size as the final published illustration. Dimensions may be given in units of length for print output (e.g. 10 × 15 cm) or pixels for on-screen viewing (e.g. 800 × 600 pixels).
Resolution is the number of dots or pixels in a given area: dots per inch (dpi) or pixels per inch (ppi) (for most practical purposes the units are interchangeable). It is very important that digital artwork be supplied at the correct resolution to ensure high-quality output—low-resolution artwork is not suitable for print, and may result in requests for resubmission and delays in publication.
Minimum resolutions (at final image size) for print:
• line artwork: 600 dpi (simple) to 1200 dpi (detailed)
• tone artwork: 300 dpi
• combined line/tone: 600–900 dpi.
Be aware that the requirements for printed and on-screen images are very different. The resolution of a computer monitor is 72–96 dpi, meaning that although an image may look acceptable on a monitor and be suitable for online use, it may be of insufficient resolution for print purposes.
Resolution is not a set value—it is variable and is inversely proportional to visual size. If the visual size is doubled, the resolution halves, reducing the quality (
Images copied from the web are usually too low resolution for print. It may be possible to obtain high-resolution versions (and appropriate copyright clearance; see
16.3.4 Handling colour
Ensuring accurate reproduction of colour illustrations is an important consideration and is critical for certain types of fine art/photography publications.
Computer monitors/desk-top printers and conventional printers use different models (colour spaces) to handle colour. Computer monitors use RGB (Red, Green and Blue) mode to display colours, whereas conventional printing uses CMYK (Cyan, Magenta, Yellow, and Key (Black) mode. As a result, an image viewed on a computer monitor may not match the final colour rendition of the printed version.
Figure 16.6 The same photograph at different resolutions.
Ideally, monitors should be calibrated to assess colour accuracy, and files should be created in the appropriate colour mode: RGB for online publication and CMYK for print publication.
16.3.5 Digital cameras
Image files of hard copy originals can be created with a good digital camera (at least 10 megapixels and a high-quality lens).
When taking digital photographs, ensure that the lighting is bright and even (without shadows), ISO is set to the lowest value, the image is sharply in focus, extraneous elements are cropped out and the camera is set to produce the largest file size possible. RAW files should be converted to a standard file format (see
Hard copy may be scanned to produce digital files. Scans should be at the final size and orientation, and at the correct resolution (see
It is better to scan originals rather than scan a printed copy, to reduce interference patterns (moiré) caused by previous screening. A high-resolution scan of a poor original will not improve the quality, although it is possible to touch-up and relabel scanned originals using image-editing software.
16.3.7 Submitting files
Check that artwork files conform to any specified requirements. Individual illustrations (and parts) should be supplied as separate files. Do not embed the illustrations in text or other files. Ensure all layered files are flattened (the layers that make up the image are compressed into a single plane).
Name the files in a logical style following the conventions used in the text (e.g. in a simple format Figure_1.1.tif or with a project identifier Smith_Fig_3.tif). If figures are not numbered, use a brief unambiguous descriptive name to match the corresponding citations and captions (e.g. Ozone_distribution_2014.tif).
Compile a separate artwork log listing all of figures (and parts) and corresponding file names, together with any notes (e.g. unusual file formats).
Final artwork files may be submitted on portable media (CD/DVD, flash drives, etc.) or over the Internet via file-sharing sites/FTP. Group large numbers of individual files in a logical directory/folder structure (e.g. by section/chapter). Keep a backup copy of all files.