What Actually Changes When You Use Exposure Compensation
Exposure compensation is one of those camera controls that feels simple on the surface—just a little dial with “+” and “–”—yet behind the scenes it works by adjusting other exposure parameters. The key point is that exposure compensation itself does not directly change the brightness of the sensor. Instead, it tells the camera to modify one or more of the core exposure settings the camera is already using.
Those core settings are the classic exposure triangle: shutter speed, aperture, and ISO. Which of these actually changes depends entirely on the shooting mode you are using.
In aperture priority mode (A or Av), you choose the aperture and the camera selects the shutter speed automatically. When you apply exposure compensation in this mode, the camera changes the shutter speed. Dialing in +1 EV makes the camera slow the shutter to let in more light. Dialing in –1 EV makes the camera use a faster shutter speed. The aperture stays exactly where you set it.
In shutter priority mode (S or Tv), you select the shutter speed and the camera adjusts the aperture. When you apply exposure compensation here, the camera changes the aperture value. Positive compensation opens the aperture (lower f-number) and negative compensation closes it.
In program mode (P), the camera controls both aperture and shutter speed. Exposure compensation shifts the program line, meaning the camera adjusts both values together while keeping the same exposure relationship.
ISO behavior depends on whether Auto ISO is active. If you are shooting in manual exposure mode but using Auto ISO—a setup many photographers prefer for events or street photography—the exposure compensation dial typically changes ISO. The camera keeps your shutter speed and aperture fixed but raises or lowers ISO to brighten or darken the image.
In full manual mode without Auto ISO, exposure compensation usually does nothing at all because the camera is no longer controlling exposure parameters. You must change shutter speed, aperture, or ISO yourself.
The lens itself rarely plays a role in exposure compensation directly. The only lens parameter involved is aperture, and even that only changes if the camera is controlling it in the chosen mode. Everything else happens inside the camera’s exposure system.
In practical shooting—especially for the kind of street and travel photography you often do—exposure compensation becomes a quick way to override the camera’s meter. Scenes with bright skies, reflections, or backlighting tend to trick the meter into underexposing the subject. A quick +0.7 or +1 EV nudges the camera to brighten the image without forcing you to change your chosen aperture or shutter settings.
So the short answer is simple but slightly deceptive: exposure compensation adjusts shutter speed, aperture, or ISO depending on the shooting mode. It never changes the lens directly, but it can change the aperture if the camera is the one controlling it.