Handling Logarithmic Scales

Failing to identify a log scale will ruin your data extraction. Here is how to handle them correctly.

Identifying a Log Scale

A linear scale has equal physical distance between equal additive steps (e.g., the distance from 10 to 20 is the same as 20 to 30).

A logarithmic scale has equal physical distance between equal multiplicative steps (e.g., the distance from 10 to 100 is the same as 100 to 1000). Tick marks within a log cycle (1, 2, 3... 9) get physically closer together as the value increases.

Not sure? Use our Log Scale Verifier tool.

Calibration Math

When you tell GraphScreen an axis is Log(Base 10), the interpolation formula changes from:

Value = m * Pixel_X + b

To:

Value = 10 ^ (m * Pixel_X + b)

Common Mistakes

• Calibrating at 0: Log scales cannot start at 0 (log(0) is undefined). If the axis starts at 0.1, calibrate X1/Y1 to 0.1, not 0.
• Natural Log vs Base 10: Most visual charts use Base 10. Natural log (e) is rarely used for display axes unless explicitly labeled `ln(y)`.