m of Natural History
Department of Paleobiology
National Museum of Natural History
Smithsonian Institution
Illustration Care
Illustration Techniques - page 1 2 3 4 5 6 7 8 9 10 11

Conventions in scientific illustration
There are a number of conventions used in scientific illustration, and each scientific specialty (as well as each publication) usually has specific conventions of its own. The conventions were developed to help the reader more easily understand the information presented in the drawings.


Specimens should be lit with a raking light shining from the upper left at a 45° angle. Standardizing the light source helps the reader understand the three-dimensional shape of an object. The harsh raking light accentuates the object's light and dark areas and helps indicate form and structure.

The photographs at the left show the importance of this convention. Only by knowing the direction of the light source will the reader of this page know whether the fossil beetle carapace is covered with bump or pits.


Photo of Eocene Green River Formation fossil beetle by Dan Behnke courtesy David Kohls and Conrad Labandeira. Copyright Dan Behnke.

Shading is the most important tool for giving a two-dimensional drawing the appearance of having three dimensions. The figure to the right shows how shading turns a flat circle (lower photo) into a sphere (upper photo).

The numbers on the upper green sphere indicate the basic formula for shading objects with light coming from the upper left. 1) is the highlight, or lightest light; 2) shows the intermediate tone; 3) shows the core shadow - or darkest dark; and 4) shows the reflected light coming from underneath the object. This formula can be applied to the shading of all objects.

The photo on the bottom shows a circle with no variation in shading. It appears to be completely flat.


Green sphere and circle illustrate shading concepts.

Reproducing the illustration
The artist should measure the page size and column width of the publication in which the new illustration will appear prior to beginning the drawing (if it is known where the illustration will be published). The illustrator should plan the original drawing so that it will be reproduced at 66% or 50% of its original size so that it looks its best in publication. Enlarging a drawing will magnify any imperfection in the drawing. Final size or use of the printed piece will determine the line width used, ppi selected in computer art, and other important factors.

The figure number and author's last name should be included on each illustration, usually in the lower right hand corner. Notes to the printer should be written in the lower margin, far from the image area. Any notes to the printer should be clear and easy to understand.

Most journals prefer to receive electronic files rather than original art. Scan continuous tone work (black and white, or color) at 350 ppi (pixels per inch) with the image scanned at the final printed size.

Scan line art or stipple drawings at 1200 ppi (with the image scanned at the final printed size) in grayscale. The image should then be corrected for proper contrast. Finally, the art should be converted to bitmap to reduce the size of the final file.

If your art will appear on a website, it should be scanned at 72 ppi (with the image scanned at the final published size).

Contact your printer or publisher if possible to find out what they need in order to have the best print job possible. Many printers and journals publish prepress printing advice and recommendations online.

Draw what the author needs to show

Elegant drawings showing all the texture, pattern, tone and shade, and proper perspective in a specimen can be useful, but at times a simple line drawing better serves the purpose for which a scientific illustration is needed. This can be a disappointing realization for a talented artist who longs not only to portray a subject in all its beauty, but to also show their abilities as an artist. If, for example, the point of the drawing is to show the sutures of the skull that are nearly invisible in the skull itself because of artifacts of age (and have taken the scientist many months to decipher), then it would be a waste of journal space and the readers' time to have the sutures obscured in the scientific illustration even if the distracting elements would make the drawing more aesthetically beautiful. Likewise, if a paleobotanist wants to illustrate the veins of a fossil leaf, a simple diagrammatic line drawing may work better than an exquisite tone drawing of the fossil leaf.

Illustration Care