Changing the brightness
Fine-tune your images with a dose of exposure compensation
Although it can be useful for the camera to automatically choose the shutter speed when you set an aperture in Av mode, or select an aperture when you’re setting the shutter speed in Tv mode, this does rely on the camera having determined what the best exposure is to begin with. But this isn’t always the case. When there’s a bright light source in the frame, or the scene is mostly pale or dark – even when light levels are low – your camera can be fooled into under or overexposing a shot. Trying to rectify things by adjusting the aperture, shutter speed or ISO will have no effect in these modes. The camera will just make an adjustment in the opposite direction with one of the other variables.
There are two options here: use exposure compensation or switch to Manual mode and dial in the combination of aperture, shutter speed and ISO that will give you the result that you want.
Exposure compensation can be set in the camera’s main menu, or the Quick Control screen. Some cameras enable you to change the compensation amount directly by rotating the Quick Control dial on the back of the body, while others require the ‘Av+/-‘ button to be pressed before turning the main dial.
Keep an eye on the shutter speed as you make changes in Av or P mode, as the shutter speed may become too slow for sharp shots. If you have Auto ISO set, then the ISO will be adjusted instead – if this goes too high you’ll end up with more noise in your pictures.
Exposure compensation doesn’t work in Manual, but you can change the aperture, shutter speed or ISO – or a combination of them – to obtain the desired exposure. If you have Auto ISO set, then the camera will alter the ISO to maintain the original exposure even if you set a different aperture or shutter speed, so it’s best to manually set an ISO.
Aperture Priority With a constant aperture of f/9 and an ISO of 400, it’s the shutter speed that’s shifted when exposure compensation is used in Av