Use exposure compensation at capture when the meter would otherwise give you the wrong exposure. It is not just post-processing.

In aperture-priority, shutter-priority, or program modes, exposure compensation tells the camera to change the actual exposure parameters—typically shutter speed and/or aperture (and sometimes ISO if auto ISO is involved). That changes how much light reaches the sensor.

That matters because software cannot recover everything later. If highlights are clipped or shadows are badly underexposed, you may lose detail, increase noise, or affect motion blur and depth of field in ways post-processing cannot fully fix.

A RAW editor’s exposure slider is different: it adjusts the recorded data after capture. It can help, especially with RAW files, but it cannot restore information that was never captured within the sensor’s dynamic range.

So the general rule is:

• use exposure compensation to get the exposure you want in-camera
• use software later for refinement

This is why exposure compensation is one of the most commonly used controls on a camera.