Background

Images are often used to share scientific data, providing the visual evidence needed to turn concepts and hypotheses into observable findings. While many resources exist regarding guidelines on fraudulent image manipulation and technical requirements for image acquisition and publishing, data examining the quality of reporting and ease of interpretation for image-based figures are scarce.Moreover, recent evidence suggests that important methodological details about image acquisition are often missing. Although general recommendations emphasize that authors should design figures for their audience rather than themselves, and that figures should be self-explanatory, figures are often difficult to interpret, and therefore represent a problem for accessibility and importantly, for reproducibility. In their work, Jambor et al (1) (as part of the eLife Ambassadors program of 2018 and 2019) examined the quality of reporting and accessibility of image-based figures among papers published in top journals in plant sciences, cell biology and physiology. Based on their results, they provide targeted recommendations about how informative image-based figures can be created in a manner that makes them both accessible and reproducible.

 

Key findings and developments

Findings regarding image-related information across three fields: plant science, physiology and cell biology.

The authors focused on papers from the top 15 journals within three large research fields, namely plant sciences, cell biology and physiology. These were the key findings:

1. Scale bars: 50% of papers approximately, had complete scale bars for each image provided, while the remaining 30% and 20% had incomplete or fully missing information, respectively.
2. Insets: The majority of papers in all three fields clearly and accurately marked the location of all insets, however, one-fifth of papers appeared to have marked the location of at least one inset incorrectly, while in approximately one-fifth, clear inset markings were missing for some or all insets.
3. Accessibility to readers with colour blindness: Although papers without any colorblind accessible figures were uncommon, almost half of cell biology papers and 1/4^th of physiology and plant science papers contained some images that were inaccessible to readers with deuteranopia. Further, up to a third of papers contained color annotations that were not visible to someone with deuteranopia.
4. Figure legends: The majority of physiology and cell biology papers provided a full description of the objects shown in the figure. About half of the papers also failed to adequately explain insets. About 66% of all papers clearly stated the meaning of all image labels, and the vast majority explained what each colour represented.
5. Based on all criteria defined in this study, the authors found that only 16% of physiology papers, 12% of cell biology papers, and 2% of plant science papers, met the criteria for all image-based figures in any given paper.

Based on the above findings, the authors provide a set of recommendations for creating clear and informative image-based figures for scientific publications.

 

Recommendations for creating clear and informative image-based figures for scientific publications.

1. Choose a scale or magnification that fits the research question. Namely, that it allows to see the features described and needed to answer the question- be this anywhere in the range between whole body level and sub-cellular level. When both low and high magnifications are necessary for one image, insets should be used to show a small portion of the image at higher magnification, and the inset location should be accurately marked in the low magnification image. Also, insets should be explained in the figure legends.
2. Include a clearly labeled scale bar. The authors offer various suggestions of what a clearly labeled scale bar should include: every image type should have a scale bar; these scale bars and labels should be clearly visible; the dimensions should be stated with the scale bar.
3. Use colours wisely. In a scientific context, adapting colours is possible and may enhance readers’ understanding. In many instances, scientists can choose between displaying greyscale or colour images. Greyscale is often used to display fine details, or when visibility is compromised.
4. Choose a colourblind accessible colour palette. Colourblind-safe colour palettes for fluorescence and other images should be used – there are programs simulating how a specific combination of colours would look to readers with deuteranopia (who cannot distinguish red and green), and tritanopia (who cannot distinguish green and blue). The authors recommend the use of free tools for this, such as Color Oracle. The authors suggest that cyan and magenta, or green and magenta are combinations visible to readers with normal vision, deuteranopia and tritanopia. In addition to choosing an adequate colour palette, information can be displayed in separate channels in addition to the merged image. Individual channels may be shown in greyscale to make it easier for readers to perceive fine details.
5. Figure design. In multi-pannel figures, careful planning is needed to convey a clear message, while ensuring that all panels fit together and follow a logical order. The authors provide in their work a planning table to help with figure design. They highlight as an important aspect, the direction of information depending on their array of columns/rows, and how readers approach this information (i.e. top to bottom/left to right). The authors suggest QuickFigures as a tool that helps create multipanel figures for microscopy-based images.
6. Figure annotation. The image should have the right amount of annotations, without it being too little, too abstract, or too long such that it covers the image and/or results in a label difficult to interpret. In such case, explanations of the labels should be placed in the figure legend. Additionally, abbreviations should be used cautiously, and should be explained in the figure legend even if they are defined within the manuscript. Also, colours and stains should be explained enough to allow readers unfamiliar with the stain to interpret the image. Finally, ensure that the annotations (in addition to the figures) are accessible to colour-blind readers.
7. Prepare figure legends. Important information needed to interpret the images should be present in the legend. This includes species and tissue type/object shown in the figure, explanations of all labels, annotations and colours, and markings/legend entries denoting insets. Moreover, relevant details not marked in the figure should be explained in the legend.

What I like about this preprint

I think this work is extremely useful as a very complete guideline to all researchers in various areas beyond the three chosen in this study. I think indeed, following these recommendations carefully will improve a lot the readability and reproducibility of imaging-based work. In my experience, imaging-based labs are familiar with the vast majority of these recommendations. I think having these recommendations is a good baseline for all labs (including those whose expertise is not imaging) to standardize figure generation when it comes to inclusion of images. Moreover, the work touches on the rationale for each of the recommendations they give.

References

1. Jambor et al, Creating clear and informative image-based figures for scientific publications, bioRxiv, 2020.

 

 

 

doi: https://doi.org/10.1242/prelights.26207

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