Previous Meetings: Preparing Digital Images for Publication :: Microscopy Group - Biomedical Imaging Unit - Research - Faculty of Medicine - University of Southampton, Faculty of Medicine

Pixels: digital images are arrays of numbers (pixels) - signal intensity is recorded for each point (pixel) in an image
Resolution: more pixels = higher resolution, but is ultimately limited by the resolution of the collection device
More pixels = larger files
Bit depth: The range of intensity values possible - this determines the number of shades of grey in greyscale images
Typically 256 shades of grey, stored as an 8 bit binary number (2⁸ = 256)
Greater colour depth (eg 12 bit = 4096 shades) records a wider range of intensities (often stored as 16 bit images)
Not all image viewing software can handle 16 bit greyscale images and you may need to convert down to 8 bit
Colour is recorded as combinations of colour values at each pixel:
- RGB (red/green/blue) - 24 bit colour is 8 bit red + 8 bit green + 8 bit blue (256³ colours)
- CMYK (cyan/magenta/yellow/black) - predominantly used for printing so may be requested by journals

(recommendations taken from Journal of Cell Biology guide lines)

… be aware of the resolution at which the image was acquired
…(do) not set the total number of pixels to be greater than that in the original image; otherwise, the computer must create data for you … the resulting image is a misrepresentation of the original … (therefore when capturing images have a mind for what you need to use them for)
…It is acceptable to reduce the number of pixels in an image… Although this does alter your original data, you are not creating something that was not there in the first place; you are presenting an average.

Pixels are your original data!

Always keep your original image - this is your raw data, your reviewers might ask to see it!
You are presenting your data to allow readers/ viewers to
- see the points you are making in the text
- assess the quality of the data
- extract further information now or in the future
What is it not fair to do:
- select rare or unrepresentative events
- modify the original so as to change the interpretation
- add or delete elements that are important in the interpretation

Read the instructions!
Follow them exactly!
Resolution: journals usually specify an image resolution (dots (pixels) per inch, often 300 dpi, sometimes 600 dpi). Make sure that your original images are compatible with these requirements
Number of figures: “Figures should be limited to a total number of 7 and no more than two journal pages, including legends.” (ATS - however the availability of online supplementary information makes this less important, and allows you to show movies etc.
Legends should be in the text, not in the figure image files
“all figure titles and explanations of symbols should appear only in the figure legend , not in the actual figure.” (ATS)
Labels- follow the instructions to the (capital or small) letter (or number)!
Prepare figures at the final size of the journal page
“Figures should not exceed the page dimensions of 17.4 x 21.3 cm (6 7/ 8 x 8 3/ 8 inches); single-column figures should not exceed 8.4 x 21.3 cm (3 5/ 16 x 8 3/ 8 inches); and double column figures should not exceed 17.4 x 21.3 cm (6 7/ 8 x 8 3/ 8 inches). It is preferred that figures be submitted at final size. Light and electron micrographs should be composed to fill the width of either a single or double column.”
Note that different Journals will have different requirements, if a manuscript gets rejected and is then resubmitted elsewhere, you may have to reformat the figures
Don’t scan images if avoidable

What's in a picture? The temptation of image manipulation.
Seeing is believing? A beginners' guide to practical pitfalls in image acquisition.
Editorial instructions for JCB - note the section on post-acceptance scrutiny of images
JCB DataViewer, a browser-based application for viewing original image files

University of Southampton