H-D Curve Tool

Plots H-D curves (film characteristic curves) and calculates key metrics from density readings from a 31 step, step-wedge and density readings from film exposed using the same step-wedge. Supports multiple film files for comparison.

Default: stouffer-31-step-wedge-2025-09-26.txt and T-Max 400 XTOL series (loaded automatically)
Select one or more film density files to plot multiple curves
Format details
  • Step-wedge density file: 31 densities, one per line, in order, starting with step 1 (the highest density step).
  • Film density files use extended format with labeled sections:
    • All metadata can be placed at the top in any order, including base_fog:, dmax:, and illuminance measurements
    • Step densities must be labeled with step_densities: followed by 31 density values, one per line
    • Multi-line fields: notes: and step_densities: capture all following lines until the next key-value pair
  • Required metadata keys: base_fog, dmax, e_ref_min, e_ref_max, t
  • Optional metadata keys: date, test_number, film, film_roll, film_expire_date, procedure, developer, dev_temp_start, dev_temp_end, dev_time, air_temp, water_bath_temp, water_bath_setpoint, rinse_water_temp, e_ref_offset, logh_offset, notes, step_densities
  • Exposure calculation: logHmax = log₁₀((e_ref_min + e_ref_max)/2 + e_ref_offset) × t) + logh_offset
  • Comments: Lines starting with # are ignored. Inline comments after # are stripped from data.
  • Lines may include comments after #; blank lines are ignored.
  • For each step i: logH[i] = logHmax − Dwedge[i].
StatusWaiting for files…
X range (logH)
Y range (Density)