We probe the dust extinction through the foreground disk of the overlapping galaxy pair UGC 5041 by analyzing B , I , and H band images .
The inclined foreground disk of this infrared-selected pair is almost opaque in B at a projected distance of \sim 8 kpc .
From the images , we estimate directly the area-weighted distribution of differential near-IR extinction : it is nearly Gaussian with \langle \tau _ { I } - \tau _ { H } \rangle = 0.6 and \sigma = 0.27 .
For a homogenous dust distribution and a Milky Way extinction curve , this corresponds to a face-on distribution p ( \tau ) with a mean of < \tau _ { V } > = 0.34 and \sigma _ { V } = 0.15 .
For a clumpy dust model the optical depth estimate increases to < \tau _ { V } > = 0.41 and \sigma _ { V } = 0.19 .
Even though the galaxy pair is subject to different selection biases and our analysis is subject to different systematics , the result is consistent with existing case studies , indicating that < \tau _ { V } > \sim 0.3 is generic for late-type spirals near their half-light radii .

We outline how to estimate from p ( \tau ) by how much background quasars are underreresented , where projected within \sim 10 kpc of nearby spirals , such as damped Ly- \alpha absorbers or gravitational lenses ; from our data we derive a factor of two deficit for flux-limited , optical surveys .