Moving the histogram
How to shift the position of the histogram and fine-tune the brightness of your pictures
When you take pictures using your camera’s semi-automatic shooting modes, such as Aperture Priority or Shutter Priority, changing the camera settings will have no effect on the overall brightness of an exposure. The camera will simply compensate for any change you make to the aperture, shutter speed or ISO so it can maintain the exposure it thinks is correct.
To override the camera, you’ll need to use exposure compensation. Use negative exposure compensation to shift the histogram to the left for a darker exposure, or positive exposure compensation to shift it to the right for a brighter exposure.
If you’re using Manual mode, changing the aperture, shutter speed or ISO will have an effect on the exposure and the position of the histogram. For instance, if you increase the exposure by setting a slower shutter speed, a larger aperture or a higher ISO , you should see the histogram move to the right. The setting or combination of settings you change to increase or decrease the exposure will be determined by the effect you’re looking for in your picture. You can see what happens when you shift the settings in Manual mode in our diagram here…