The primary purpose of each of the legs in the Exposure Triangle is to obtain a properly-exposed image.\u00a0 Each of the legs can be adjusted to obtain a good exposure.\u00a0 One has a great deal of freedom in choosing these settings: one can move up one leg if ones moves down another and still get a well-exposed image.<\/p>\n
Each part of the Exposure Triangle can be measured in something called \u201cstops.\u201d\u00a0 One stop changes the exposure by a factor of two, brighter or darker.\u00a0 If you change the exposure by two stops, you have changed the brightness by two factors of two, that is, by a factor of 4.\u00a0 If you change the exposure by three stops, you have changed the brightness by a factor of 8 (2x2x2).<\/p>\n
The reason why we use the word \u201cstop\u201d is obscure, but it will be explained (if you care) in the aperture section.<\/p>\n
Here is a cheat sheet for the use of the term \u201cstop\u201d.<\/p>\n
Etc.<\/em><\/td>\n<\/tr>\n| -3 stops<\/td>\n | Eight times darker<\/td>\n<\/tr>\n | -2 stops<\/td>\n | Four times darker<\/td>\n<\/tr>\n | -1 stop<\/td>\n | Two times darker<\/td>\n<\/tr>\n | 0 stops<\/td>\n | Exposed properly<\/td>\n<\/tr>\n | +1 stop<\/td>\n | Two times lighter<\/td>\n<\/tr>\n | +2 stops<\/td>\n | Four times lighter<\/td>\n<\/tr>\n | +3 stops<\/td>\n | Eight times lighter<\/td>\n<\/tr>\n | Etc.<\/em><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n | \n |