Un­der­stand yo ur histo grams

Dis­cover why the bright­ness his­togram takes the heat out of man­ual ex­po­sures

Digital Camera World - - BACK TO BASICS -

US­ING spot me­ter­ing and the ex­po­sure indicator in the viewfinder, you can set the ex­po­sure based on a

spe­cific part of the scene. But the his­togram shows you the ex­po­sure for the whole im­age. By re­view­ing the his­togram af­ter you’ve taken a shot (or check­ing the live his­togram, if avail­able), you can see whether you’re mak­ing full use of the cam­era’s imag­ing sen­sor and if any ar­eas are go­ing to lose de­tail. Re­mem­ber that the his­togram is based on a JPEG ver­sion of the im­age and the cam­era set­tings made at the time; if you shoot raw, then you’ll have more head­room to fine-tune the ex­po­sure with com­pen­sa­tion later, when you process the shot.

As in­di­cated on the pre­vi­ous page, you can’t use ex­po­sure com­pen­sa­tion in Man­ual mode, al­though some cam­eras let you do so when you use Auto ISO. This is be­cause in Auto ISO, the cam­era will change the ISO to en­sure that the aper­ture and shut­ter speed that you’ve di­alled in de­liver what it de­ter­mines to be a good ex­po­sure; chang­ing the aper­ture or shut­ter speed to in­crease or de­crease the ex­po­sure will sim­ply re­sult in the cam­era al­ter­ing the ISO to com­pen­sate for the change you made! To make the im­age brighter or darker, you need an op­tion to dial in ex­po­sure com­pen­sa­tion.

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