Reflectance/Transmittance Calculator

Integrating sphere measurements of reflectance and transmittance use a substitution method: the sample signal S_sample is ratioed against a reference signal S_ref from a standard with known reflectance ρ_ref (or transmittance T_ref), giving the raw sample value as ρ_sample = ρ_ref × (S_sample/S_ref). Accuracy degrades when sample and reference reflectances differ significantly, because port losses — the fraction of sphere flux that escapes through the illumination and sample ports — shift with each substitution. The optional port-loss correction applies the generalized integrating-sphere model (Goebel 1967), requiring sphere wall reflectance ρ_w, total port fraction f, and sample port fraction f_s. Enter reference standard values, measured signals in volts, and enable the correction to see the corrected value and the magnitude of the correction. The tool supports both reflectance and transmittance measurement geometries.