Structural rule A famous structural rule is known as cut. Considerable effort is spent by proof theorists in showing that cut rules are superfluous in various logics. More precisely, what is shown is that cut is only (in a sense) a tool for abbreviating proofs, and does not add to the theorems that can be proved. The successful 'removal' of cut rules, known as "cut elimination", is directly related to the philosophy of "computation as normalization" (see Curry–Howard correspondence); it often gives a good indication of the complexity of deciding a given logic. Structural rule In proof theory, a structural rule is
Sunny 16 rule is to set shutter speed nearest to the reciprocal of the ISO film speed / setting and f-number according to this table: This is a scene of average brightness, in direct sunlight. It was shot at ISO 100, f/8 at 1/400 second - the recommended "sunny 16" exposure (which is what autoexposure gave). Sunny 16 rule In photography, the sunny 16 rule (also known as the sunny rule) is a method of estimating correct daylight exposures without a light meter. (For lunar photography there is a similar rule known as the looney 11 rule.) Apart from the obvious advantage of