Macro Reproduction Ratio Measurement Calculator

Method, formula and assumptions

Reproduction ratio = active sensor width/object span across the complete image. Object pixels/mm = recorded width/object span. Multiply by feature width; invert the density for object micrometers/pixel.

Input definitions and supported units

• Active recorded sensor width (mm): Measured or assumed numerical value, from 0.1 to 100; must be positive.
• Object ruler span across full frame (mm): Measured or assumed numerical value, from 0.01 to 100000; must be positive.
• Recorded image width (pixels): Whole-number count, from 1 to 1000000; must be positive.
• Object feature width (mm): Measured or assumed numerical value, from 0 to 10000; zero is supported where the stated method permits it.

Worked example with answer

A 36 mm active sensor framing a 24 mm ruler span gives 1.5x reproduction. At 6,000 pixels it records 250 pixels/mm; a 0.2 mm feature spans 50 pixels and each pixel represents 4 micrometers.

How to use the results

This measures actual framing from a ruler without assuming lens focal length. Use active sensor width if a recording mode crops the sensor.

Results retain full precision internally and display up to four decimal places. Very small nonzero results use scientific notation rather than appearing as zero. Check the labels before comparing values across units.

Limitations and references

Pixel sampling is not optical resolving power. Distortion, focus, demosaicing and diffraction can prevent distinguishing a feature even when it spans many pixels.

The method is a self-contained arithmetic, geometric or explicitly stated mathematical model. There are no imported tariffs, empirical presets or equipment specifications; measured values and allowances must come from your own process.

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