Pre-submission advice:  figures

Academic publications commonly contain images, particularly in the fields of science and technology.  Figures should be of high quality, clearly readable without magnification, but without unduly inflating the file sizes. 

 

Quality

Authors naturally want to retain an appropriate image quality and resolution.  

  • Readers should not need to magnify an image in order to understand it:  it should all be readable at the same magnification as the surrounding article text.  In other words, the images should be completely readable when the document is printed on paper. 

 

Image format

  • Save as vector graphics all images containing primarily "line art" and/or text — including all graphs (bar charts, scatter plots, pie charts, etc.), technical drawings, flow charts, phylogenetic trees, and so on — as far as possible.  
    • Suitable formats may include SVG, EMF, PDF, ....  
  • Save as rasters all images that contain pixel-by-pixel renderings — as in the case of digital photographs, micrographs, screenshots, and so on — as far as possible.  
    • For rasters with many colours in gradually varying hue or saturation or brightness — as is typical for photographs — JPEG may be a suitable format.  Note that JPEG is generally a lossy format, so artefacts will be introduced, and image quality will be degraded every time the image is edited and resaved.  (Use a high "quality" parameter in the JPEG algorithm to minimise artefacts.)  Alternative formats include GIF.  
    • For rasters with a low or moderate number of colours, especially with large regions of uniform colour — as is typical for screenshots, but may also arise in the case of composite images and "line art" — compressed-PNG is a recommended format.  PNG is a lossless format, so there will be no artefacts introduced, and there will be no degradation in image quality, no matter how many times the image is edited and resaved.  Alternative formats include TIFF and BMP.  

 

File size

The above guidelines do not necessarily require large image files, nor large document files (where images are embedded). 

  • Commonly when submitting to journals the manuscript contains either no images at all, or (optionally) images of moderate resolution.  The high-resolution images are then submitted separately as individual files.  
  • With raster images it is better to embed either BMP or compressed-PNG rather than TIFF.  In particular, don't embed TIFF images in Word documents.  Embedded TIFF image files do not get (re)compressed within the DOCX file.