Physics Engine

Calculates total photon dose needed at the physical film plane, negating manual sliding rules.

• F_F (Film Factor): Roentgens needed to achieve the target density.
• SFD_m: Distance in meters (Inverse Square Law).
• 2^(x/HVL): Continuous exponential attenuation.
• A & Γ: Source Activity (Ci) and Gamma Constant.

Isotopes (Γ)

The intrinsic radiation output (R·m²/hr·Ci).

• Ir-192 (Γ = 0.48)
  Standard. Steel 12-63mm. Avg ~380 keV.
• Se-75 (Γ = 0.203)
  Thin wall pipe. Smaller barricades. Avg ~220 keV.
• Co-60 (Γ = 1.30)
  Heavy castings/concrete. Avg ~1.25 MeV.

Film Classes

Finer grain yields higher detail but demands exponentially more dose.

Density: Typically 2.0 to 4.0. Adjusting density multiplies the base required Roentgens linearly.