for sure. OVER exposure is as much of a problem as under. The oft swallowed mantra of rating HP5/TriX at 160-200 might work fine in strong sidelight in the mexico desert but shooting in britain, where sunshine occurs only when the unicorns run free, it is often necessary to rate at bos speed and sometimes to underexpose and seriously up the devt.

In Afghanistan, i rate most films quite low, bec I have very contrasty lenses (ZMs) and the light can be harsh. Back in the UK, I am happy to increase my film speed by 2/3 stop under average conditions so I get some dark values!