  Differential $E_{V-I}$ variations of up to $\sim 0.2$ mag on a scale of
arcminutes across NGC 3201 are presented in the form of an extinction map. This
map, created by calculating average $E_{V-I}$ values for stars in small
subregions of the field with respect to a fiducial region, greatly improves the
appearance of the CMD of the cluster. We describe how we implemented this
technique in detail with our data for NGC 3201. A comparison between our map
and that of the same region extracted from the COBE/DIRBE reddening maps
published by Schlegel, Finkbeiner, & Davis (1998) (SFD) displays larger-scale
similarities between the two maps as well as smaller-scale features which show
up in our map but not in the SFD map. Several methods of determining an
$E_{V-I}$ zeropoint to add to our differential extinction map are presented.
Isochrone fitting proved to be the most successful one, but it produces an
average $E_{V-I}$ for the cluster which is smaller than previously published
values by $\sim 1.5\sigma$. Finally, our results seem to support the statement
by Arce & Goodman (1999) that the SFD maps overestimate the reddening in
regions of high extinction.
