Exposure Compensation

Expo­sure com­pen­sa­tion allows you to adjust the expo­sure lev­el set by your cam­er­a’s auto­mat­ic set­tings. It’s par­tic­u­lar­ly use­ful when pho­tograph­ing very bright or dark sub­jects, high-con­trast scenes, or in sit­u­a­tions with strong back­light­ing, all of which can mis­lead your camera’s auto-expo­sure sys­tem into set­ting expo­sure val­ues that don’t accu­rate­ly rep­re­sent what you saw. White sand beach­es and snow-cov­ered land­scapes are com­mon sce­nar­ios where cam­eras can mis­cal­cu­late expo­sure. These scenes often fea­ture high-reflectance sur­faces that are even­ly dis­trib­uted across the frame, and because the camera’s reflect­ed-light meter aims to ren­der sub­jects as mid­dle grey, the result­ing pic­tures are often under­ex­posed. Expo­sure com­pen­sa­tion allows you to use your bet­ter judg­ment to over­ride the camera’s auto-expo­sure set­tings in sit­u­a­tions where errors are like­ly.

On most cam­eras, expo­sure com­pen­sa­tion is acti­vat­ed by a ded­i­cat­ed but­ton marked with a square icon fea­tur­ing a black-on-white “+” (plus) and a white-on-black “–” (minus). Press­ing the but­ton and rotat­ing the appro­pri­ate dial lets you set the desired lev­el of expo­sure com­pen­sa­tion. (The exact pro­ce­dure varies by cam­era, so refer to your user guide.) The amount of expo­sure com­pen­sa­tion you set is dis­played either by the posi­tion of the expo­sure lev­el indi­ca­tor or as a num­ber, both of which rep­re­sent units of EV (expo­sure val­ue). Typ­i­cal­ly, expo­sure com­pen­sa­tion can be set in incre­ments of 1/3 EV, with a total range of ±2 to ±5 EV depend­ing on your cam­era mod­el.

Regard­less of your select­ed auto-expo­sure or meter­ing mode, set­ting expo­sure com­pen­sa­tion to +1 EV tells the cam­era to increase the expo­sure by one stop (i.e., one stop over­ex­po­sure com­pared to the camera’s stan­dard set­ting). Con­verse­ly, set­ting expo­sure com­pen­sa­tion to –2 EV instructs the cam­era to reduce the expo­sure by two stops (i.e., two stops under­ex­po­sure com­pared to the camera’s stan­dard).

The spe­cif­ic para­me­ters adjust­ed by expo­sure com­pen­sa­tion depend on your select­ed auto-expo­sure mode. On most cam­eras, expo­sure com­pen­sa­tion is avail­able in Pro­gram, Shut­ter Pri­or­i­ty, and Aper­ture Pri­or­i­ty modes. In Pro­gram mode, expo­sure com­pen­sa­tion is achieved by adjust­ing both the shut­ter speed and aper­ture. In Shut­ter Pri­or­i­ty mode, expo­sure com­pen­sa­tion is per­formed by chang­ing the aper­ture, and the cam­era will warn you if the com­pen­sa­tion requires an aper­ture val­ue beyond the lens’s capa­bil­i­ty. In Aper­ture Pri­or­i­ty mode, expo­sure com­pen­sa­tion is made by adjust­ing the shut­ter speed, and the cam­era should alert you if your desired lev­el of neg­a­tive com­pen­sa­tion requires a shut­ter speed faster than your camera’s capa­bil­i­ty. Expo­sure com­pen­sa­tion is not avail­able in Man­u­al mode because the user sets the shut­ter speed, aper­ture, and ISO, and there’s no auto-expo­sure pro­gram to over­ride.

Exposure compensation and metering modes

Effec­tive use of expo­sure com­pen­sa­tion requires you to antic­i­pate when your camera’s auto-expo­sure pro­gram may mis­judge expo­sure, and your choice of meter­ing mode can either help or hin­der this effort. In gen­er­al, it’s hard­er to pre­dict how much expo­sure com­pen­sa­tion a scene might need when using com­plex meter­ing modes like eval­u­a­tive, matrix, or mul­ti-pat­tern meter­ing because it’s dif­fi­cult to deter­mine which parts of a scene the cam­era will pri­or­i­tize. The need for expo­sure com­pen­sa­tion is more pre­dictable when using sim­pler meter­ing modes like aver­age or cen­tre-weight­ed meter­ing. In these modes, you can per­form a quick men­tal assess­ment of the scene’s tonal range, defo­cus your eyes or squint to get a sense of what the cam­era might aver­age out, and then apply expo­sure com­pen­sa­tion using your bet­ter judg­ment.

Spot meter­ing offers the most pre­cise method for set­ting expo­sure com­pen­sa­tion because it allows you to iso­late a sin­gle tone with­in the com­po­si­tion and adjust com­pen­sa­tion based on whether you want that tone to appear brighter or dark­er than mid­dle grey, and by how much.

Exposure compensation and skin tones

Accu­rate­ly rep­re­sent­ing skin tone and colour has been a pur­suit in pho­tog­ra­phy for decades, with many mod­ern films spe­cial­ly for­mu­lat­ed to pro­duce both accu­rate and pleas­ing results. Por­traits require par­tic­u­lar atten­tion because peo­ple are high­ly sen­si­tive to even slight devi­a­tions in skin tone and colour. If your pho­tog­ra­phy involves por­traits with peo­ple promi­nent­ly fea­tured in the frame, con­sid­er tak­ing a spot meter read­ing from the subject’s face to deter­mine the appro­pri­ate expo­sure com­pen­sa­tion. Auto-expo­sure brack­et­ing can be use­ful in these sit­u­a­tions. Gen­er­al­ly, indi­vid­u­als with light skin tones ren­der well with +1/2 to +2/3 EV com­pen­sa­tion, while those with dark­er skin tones may present best with 0 to –2/3 EV com­pen­sa­tion.

Exposure compensation and auto-exposure lock

There are sit­u­a­tions where you need to pho­to­graph mul­ti­ple sub­jects under the same light­ing con­di­tions, but the scene con­tains a vari­ety of uneven­ly dis­trib­uted tones, either on your sub­jects or their sur­round­ings. In these cas­es, the camera’s auto-expo­sure sys­tem might set dif­fer­ent expo­sure val­ues for each shot, even though the light­ing remains con­sis­tent. While you can achieve con­sis­tent and accu­rate results by set­ting expo­sure com­pen­sa­tion for each pho­to, this can become tedious. For­tu­nate­ly, there’s a more effi­cient solu­tion.

Auto-expo­sure lock (AE lock) is a fea­ture found on many DSLRs and mir­ror­less cam­eras that allows you to tem­porar­i­ly lock the camera’s auto-expo­sure val­ues. AE lock is use­ful when you plan to take mul­ti­ple pho­tos of var­ied com­po­si­tions or sub­jects under the same light­ing con­di­tions, or when the area of focus dif­fers from the expo­sure meter­ing zone. The exact imple­men­ta­tion of AE lock varies by cam­era, so refer to your user guide for details. Typ­i­cal­ly, AE lock func­tions either as a press-and-hold but­ton or as a switch. Press­ing and hold­ing the AE lock but­ton locks the expo­sure to the cur­rent set­tings as long as the but­ton is pressed. When used as a switch, the expo­sure is locked when the AE lock but­ton is pressed and remains locked until the but­ton is pressed again (or the cam­era is pow­ered off). When AE lock is used in con­junc­tion with expo­sure com­pen­sa­tion, the camera’s stan­dard auto-expo­sure val­ue is locked, but you can still adjust the over­all expo­sure by chang­ing the expo­sure com­pen­sa­tion.