In prior work, we suggested that in tissues of 5 to 10 mean free path lengths for scattering in thickness, multiply scattered photons could be deviated at angles outside the NA of the collection optics.30 Specifically, for the case of excitation becoming more proximal to the forward tissue exit, backward propagating photons would have an increasing probability of not being collected, resulting in an erroneously high F/B ratio. In our previous work,25 we included the NA in the excitation to simulate optical sectioning; however, the respective forward and backward collection apertures were not included. Here, we updated the framework to this geometry and examined the effect on the resulting F/B ratios as a function of tissue thickness. Figure 2(a) shows the simulated F/B over 100 μm with excitation for 0.5 NA and 100% collection (as was previously assumed in the simulation) assuming typical parameters for tendon at 890 and 445 excitation and SHG emission, respectively,30,43 where , , , and . Near the top entrance of the tissue (), the differences between the effective apertures are not significant but increase rapidly for excitation at greater depths. Specifically, at 100 μm into the tissue, the simulated F/B is much smaller using complete (and nonphysical) collection relative to that obtained the actual 0.8 NA by almost a factor of 1.5 (7 versus 11) due to missed photons in the backward channel. To further visualize this effect, consider the hypothetical case of 0.5 NA collection, where we observe apparent increasing (and artifactual) F/B near the bottom exit of the tissue as more backward propagating photons fail to become collected within this aperture. Thus, even for a relatively thin tissue of 100 μm of thickness, corresponding to mean free path lengths for scattering in tendon, this shows the importance of including the apertures within the simulation framework to accurately extract the emitted creation ratio from the experimental data.