Focus Stack Rail Step Planner

Method, formula and assumptions

Rail step = measured usable sharp depth x (1 - overlap). Include both endpoints: frames = ceil(depth range/step) + 1. Final position may pass the target slightly; settling occurs only between frames.

Input definitions and supported units

• Object depth range to cover (mm): Measured or assumed numerical value, from 0 to 10000; zero is supported where the stated method permits it.
• Measured usable sharp depth per frame (mm): Measured or assumed numerical value, from 0.001 to 1000; must be positive.
• Desired sharp-depth overlap (%): Measured or assumed numerical value, from 0 to 99; zero is supported where the stated method permits it.
• Exposure per frame (seconds): Measured or assumed numerical value, from 0 to 10000; zero is supported where the stated method permits it.
• Settling time between positions (seconds): Measured or assumed numerical value, from 0 to 10000; zero is supported where the stated method permits it.

Worked example with answer

5 mm range with 0.5 mm usable sharp depth and 50% overlap uses 0.25 mm steps and 21 frames through 5 mm. At 1-second exposures and 0.5-second settling, capture takes 31 seconds.

How to use the results

A zero-depth range still captures one frame. This plans movement using measured usable depth, rather than assuming theoretical depth of field matches stacking needs.

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

Focus breathing, changing magnification, subject movement and rail backlash affect merge success. No stacking-software quality or optical sharpness guarantee is implied.

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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