Allowed photometric parameter space in the (b, B₀) plane at fixed laboratory geometry (i₀, e₀, g₀) = (30^∘, 0^∘, 30^∘). Colors represent the misfit ﹩{\mathrm{log}}_{10}{\chi }^{2}﹩ between the model reflectance and a reference laboratory reflectance r_target. Instead of a localized solution, the allowed parameter space forms an extended valley, demonstrating that multiple photometric solutions reproduce the same single-geometry laboratory spectrum. The red point marks the reference parameter combination used to define r_target; it is not a uniquely recovered solution. The white curve marks the analytic locus defined by r(i₀, e₀, g₀) = r_target, along which multiple photometric solutions reproduce the same single-geometry reflectance.