Photosphere of the selected disk model SP1 (R_in = 38 AU, R_out = 198 AU, ^H/r = 0.07) at λ = 5.0 μm and with two different disk masses. The gap is detectable in the scattered light if the gap is traced by a variation of the gradient in the radial direction of the vertically integrated optical depth. This is only the case for a disk mass equal or below 2.7 × 10^-4 M_⊙, as shown on the bottom.