The character Lew Harper is based on novelist Ross Macdonald's character Lew Archer. The name was changed for the film supposedly because Paul Newman had recently enjoyed success with Hud (1963) and the producers wanted the movie's title to begin with "H". Also, the Macdonald estate did not want the name "Archer" used in the movie.
Average Shot Length = ~8.5 seconds. Median Shot Length = ~7.9 seconds.
The opening credits sequence (where Harper makes himself a terrible cup of coffee, among other things) was written and shot after the first cut of the film had already been delivered to the studio.