How to Set a Proportional Divider
Proportional dividers are drafting tools that allow the proportional transfer of dimensions for a source (a drawing, photograph or real life, as examples) to a new drawing. This can be either a expansion or reduction, depending on how the divider is used. Draftsmen require devices that are quite accurate with the ability to set specific ratios. Artists don't require the same level of precision, and more inexpensive dividers are available for sketching.
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Instructions
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Set your proportion ratio by adjusting the center pivot point on the dividers. The pivot point must remain constant so each measurement is proportional to previous. While draftsmen may need to set ratios with precision, an artist can use any setting that is convenient to the worksheet upon which they draw. The pivot will be to one side of the center of the dividers.
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Measure using the short side spread of the dividers to enlarge what you view in your reproduction. Measure using the long side spread to reduce what you view. If you are working from a photograph, for example, adjust the points of the divider on the short end to the length of an important line in the photo. The points at the long end are now set to the proportional length of that line for you to draw. The long side might be used if you are drawing an office tower in real life, with the short side providing your sketch dimension.
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Continue to transfer measurements made this way to your sketchpad or canvas. Once key dimensions are transferred, connections and details can be added freehand. Additional measurements and proportions can be verified with the dividers as long as the pivot point has not been changed.
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Tips & Warnings
When drawing from real life, use a consistent distance when setting the dividers. Holding them at maximum arm's length is reliable.
References
- Photo Credit Goodshoot/Goodshoot/Getty Images
