  We have applied Alard's image subtraction method (ISIS v2.1) to the
observations of the globular clusters NGC 6388 and NGC 6441 previously analyzed
using standard photometric techniques (DAOPHOT, ALLFRAME). In this reanalysis
of observations obtained at CTIO, besides recovering the variables previously
detected on the basis of our ground-based images, we have also been able to
recover most of the RR Lyrae variables previously detected only in the analysis
of Hubble Space Telescope WFPC2 observations of the inner region of NGC6441. In
addition, we report five possible new variables not found in the analysis of
the HST observations of NGC 6441. This dramatically illustrates the
capabilities of image subtraction techniques applied to ground-based data to
recover variables in extremely crowded fields. We have also detected twelve new
variables and six possible variables in NGC 6388 not found in our previous
ground-based studies. The revised mean period for RRab stars in NGC 6388 is
0.676 day, while the mean period of RRab stars in NGC 6441 is unchanged at
0.759 day. These values are among the largest known for any galactic globular
cluster. Additional probable type II Cepheids were identified in NGC 6388,
confirming its status as a metal-rich globular cluster rich in Cepheids.
