  We use deep, five band (100-500um) data from the Herschel Lensing Survey
(HLS) to fully constrain the obscured star formation rate, SFR_FIR, of galaxies
in the Bullet cluster (z=0.296), and a smaller background system (z=0.35) in
the same field. Herschel detects 23 Bullet cluster members with a total SFR_FIR
= 144 +/- 14 M_sun yr^-1. On average, the background system contains brighter
far-infrared (FIR) galaxies, with ~50% higher SFR_FIR (21 galaxies; 207 +/- 9
M_sun yr^-1). SFRs extrapolated from 24um flux via recent templates (SFR_24)
agree well with SFR_FIR for ~60% of the cluster galaxies. In the remaining
~40%, SFR_24 underestimates SFR_FIR due to a significant excess in observed
S_100/S_24 (rest frame S_75/S_18) compared to templates of the same FIR
luminosity.
