message: No reason to limit this to float
diff: @@ -123,7 +123,7 @@ inline vector<3, T> spd_to_rgb(SPD const& spd, T lmin = T(400.0), T lmax = T(700
  T z(0.0);
  T n(0.0);
  - for (float lambda = lmin; lambda <= lmax; lambda += step)
  + for (T lambda = lmin; lambda <= lmax; lambda += step)
  {
  auto p = spd(lambda);
  