Flash Motion Freeze Pixel Budget Calculator

Method, formula and assumptions

For m/s speed and millisecond duration, numerical subject travel is speed x duration in mm. Multiply by object-plane pixels/mm for smear. Maximum duration = allowed pixels/(speed x density).

Input definitions and supported units

• Subject transverse speed (m/s): Measured or assumed numerical value, from 0 to 10000; zero is supported where the stated method permits it.
• Measured useful flash duration (ms): Measured or assumed numerical value, from 0.000001 to 1000; must be positive.
• Object-plane sampling (pixels/mm): Measured or assumed numerical value, from 0.001 to 1000000; must be positive.
• Chosen maximum blur (pixels): Measured or assumed numerical value, from 0.001 to 1000000; must be positive.

Worked example with answer

1 m/s motion during a 0.5 ms flash travels 0.5 mm. At 10 pixels/mm that is 5 pixels smear. A two-pixel target requires 0.2 ms or less, leaving a -3 pixel margin at the entered duration.

How to use the results

Use an appropriately measured flash duration and actual object-plane scale. Ambient-light exposure can add a second, longer motion trail.

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

Flash t.1 and t.5 duration definitions are not interchangeable. Pulse shape, acceleration, ambient contribution and perspective are excluded.

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.

Related planning tools

• Shutter Angle Exposure Calculator
• Rolling Shutter Motion Skew Calculator
• Point Light Distance Exposure Compensation Calculator

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