Use rational exponent form in "ZCAM" inverse colour appearance model.
@@ -676,7 +676,7 @@ def ZCAM_to_XYZ(specification,
# Step 4 (Inverse) - Computing redness-greenness (:math:`a_z`), and
# yellowness-blueness (:math:`b_z`).
# C_z_p_e = 1.3514
- C_z_p_e = 1.351351351351351351
+ C_z_p_e = 50 / 37
C_z_p = spow((M_z * spow(I_z_w, 0.78) * F_b ** 0.1) /
(100 * e_z ** 0.068 * spow(F_L, 0.2)), C_z_p_e)
a_z = C_z_p * np.cos(h_z_r)
