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Illustrations and figures

General guidelines | File format | Figure types

EPS (Encapsulated PostScript)

Most artwork-creation applications can save in, or export as, EPS format. Please refer to the software documentation for specific instructions. Non-standard fonts should be embedded.

EPS can be used for images produced by vector-drawing applications such as Adobe Illustrator or CorelDraw. However, EPS tends to be a bulky file format, compared with PDF which is a more modern and compact functional equivalent of EPS, so submission of figures in PDF format is encouraged.

EPS images should be cropped using the same software as was used to create it (refer to the manufacturer's documentation).

If there are problems cropping the EPS image then, as a last resort, consider rasterizing it (converting from vector to bitmap format) using Photoshop, cropping the bitmap (again using Photoshop) and submitting the resulting bitmap image in TIFF or JPEG format. However, rasterization will typically increase file size and reduce quality, compared with a vector image.

PDF (Portable Document Format)

PDF is an excellent, modern image format, which can contain both vector and bitmap elements.

To ensure hiqh quality, it is vital to choose the right settings when creating PDFs. Whether using Adobe Acrobat Distiller or other tools for PDF creation, authors should choose the appropriate options to create high resolution PDFs suitable for print use. This means ensuring that all artwork within the PDF is at a suitable resolution (300 dpi or more, at the intended final size of the figure) and that any non-standard fonts are embedded.

PDF files should be compatible with Acrobat 5.0 onwards (i.e. PDF version 1.4).

Authors should ensure that PDF figures are not password protected as this prevents Chemistry Central working with the figure and can render such figures incompatible with earlier versions of Adobe Acrobat.

PDF files can easily be cropped using the full version of Adobe Acrobat. Select Crop Pages from the Document menu. The Crop Pages dialog box will appear. Change the page margins by using the up and down arrow keys for each margin (left, right, top, bottom).

Alternatively, cropping can be done by selecting the crop tool from the toolbar. Here the cropping boundaries are set by selecting a handle at a corner of the cropping rectangle, and dragging it to the correct size.

If there are problems cropping the PDF image then, as a last resort, consider rasterizing it (converting from vector to bitmap format) using Photoshop, cropping the bitmap (again using Photoshop) and submitting the resulting bitmap image in TIFF or JPEG format. However, rasterization will typically increase file size and reduce quality, compared with a vector image.

DOC (Microsoft Word)

Word is a suitable choice for submitting figures containing both vector and bitmap elements, for authors who do not have access to a specialized drawing package. Excel charts can be uploaded by embedding them within a Word file.

Figures should be prepared in Word version 5 or later, and be a single page.

DOC file should be directly uploaded into the submission system. Do not convert to JPEG or other bitmap format as this will reduce quality. Ensure that all embedded artwork is at a suitable resolution (approximately 300 dpi, when scaled to the anticipated size of the figure in the final PDF).

To crop a DOC file, select Print Layout from View pull-down menu. Next click Page Setup on the File pull-down menu and reduce the page margins (Margins tab) to zero, then change the dimensions of the page (click the Paper size tab) to match that of the image.

PPT (Microsoft PowerPoint)

Powerpoint is another good option for submitting figures containing both vector and bitmap elements, for authors who do not have access to a specialized drawing package.

Figures must be a single slide. There should be no background colour unless it is strictly necessary for the figure. The slide title or number should not be included. PPT files should be directly uploaded to the site, rather than converted to JPEG or another format that may be of reduced quality. Ensure that all embedded artwork is at a suitable resolution (approximately 300 dpi, when scaled to the anticipated size of the figure in the final PDF).

To crop a PPT file, open the View pull-down menu, ensure that the Ruler option is selected, and measure the dimensions of the image. Select all the elements in the slide and the cut these elements. Then, from the File pull-down menu, select Page Setup and change the dimensions of the slide to match that of the image. Paste the elements back into the slide.

TIFF (Tagged Image File Format)

TIFF is a bitmap format that is suitable for photographic/scanned images etc. It supports lossless compression (LZW compression) which works especially well for flat color images such as line art and screenshots.

We recommend that TIFFs are saved with LZW compression, as this allows higher resolution for a given file size. If an uncompressed TIFF is uploaded, Chemistry Central's system compresses it automatically. For this reason, the size reported for a TIFF file following upload, may be smaller than the size of the uncompressed file uploaded.

TIFF and other bitmap images can be cropped using any photo or graphics editing package, typically by selecting the area of interest and then selecting the 'Crop' option from the menu. Consult the software's documentation for further details.’ it should also say this in the last sentence of this section and of the next two sections (PNG and Bitmap).

JPEG (Joint Photographic Experts Group)

JPEG is a 'lossy' bitmap format - in order to maintain a small file size, some information in the image is discarded. In order to maintain as much image quality as possible, JPEG files should be saved at Maximum quality. See graphic below for a comparison of quality settings.

Courtesy of Bates et al., BMC Developmental Biology 2006, 6:33

Maximum-quality JPEG image

Courtesy of Bates et al., BMC Developmental Biology 2006, 6:33

Low-quality JPEG image

However, resaving low quality JPEG images with higher quality settings is not advisable, as it will only increase the file size without improving the qualityof the image

JPEG is a good choice for photographs, micrographs, autoradiographs etc. as the compression allows much higher resolution images to be submitted, for a given file size, with very little degradation of quality, provided the 'Maximum quality' setting is chosen.

JPEG is a poor choice for flat color images, line-art and screenshots as sharp edges create visible artefacts even at maximum quality settings. Such images are better submitted as TIFFs or PNGs.

Authors should minimize the number of times an altered version of an image is saved as a JPEG, as every time a modified JPEG image is saved, there is some degradation of quality. If possible, the work should be saved as a JPEG only at the end of any process of editing the figure.

JPEG and other bitmap images can be cropped using any photo or graphics editing package, typically by selecting the area of interest and then selecting the 'Crop' option from the menu. Consult your software's documentation for further details.

PNG (Portable Networks Graphics)

PNG is a modern bitmap format that is suitable for photographic/scanned images etc. It supports lossless compression which works especially well for flat color images such as line art and screenshots. One advantage of PNG compared to TIFF is that PNG images can be displayed in modern web browsers.

PNG images can be cropped using most photo or graphics editing packages, typically by selecting the area of interest and then selecting the 'Crop' option from the menu. Consult your software's documentation for further details.

BMP (Bitmap)

BMP is a Microsoft bitmap format that is suitable for photographic/scanned images etc, but is less standard and less compact than TIFF, PNG or JPEG and so is not a preferred format, although it is supported.

BMP images can be cropped using most photo or graphics editing packages, typically by selecting the area of interest and then selecting the 'Crop' option from the menu. Consult your software's documentation for further details.

CDX (ChemDraw)

CDX is the file format for saving chemical reaction schemes prepared using ChemDraw. Suggested ChemDraw settings are:

  • Chain Angle 120°
  • Bond spacing 18%
  • Fixed length 0.406 cm (11.5 pt)
  • Bold width 0.056 cm (1.6 pt)
  • Line width 0.018 cm (0.5 pt)
  • Margin width 0.046 cm (1.3 pt)
  • Hash spacing 0.071 cm (2 pt)

TGF (ISIS/Draw)

TGF is the file format for saving chemical reaction schemes prepared using ISIS/Draw.

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