Rule of thirds room should be in front of the subject with the vertical line running through their perceived center of mass. The rule of thirds was first written down by John Thomas Smith in 1797. In his book "Remarks on Rural Scenery," Smith quotes a 1783 work by Sir Joshua Reynolds, in which Reynolds discusses, in unquantified terms, the balance of dark and light in a painting. John Thomas Smith then continues with an expansion on the idea, naming it the "Rule of thirds": Two distinct, equal lights, should never appear in the same picture : One should be principal, and the
Rule of thirds (diving) Rule of thirds (diving) In scuba diving, the rule of thirds is a rule of thumb used by divers to plan dives so they have enough breathing gas remaining in their diving cylinder at the end of the dive to be able to complete the dive safely. This rule generally only applies to diving in overhead environments, such as caves and wrecks, where a direct ascent to the surface is impossible and the divers must return the way they came. For divers following the rule, one third of the gas supply is planned for the outward journey, one third is