Issue:

My rendering is too bright or too dark

Cause and Solution:

If your rendering is under- or overexposed, this may be caused by:

Wrong exposure parameters
To fix this, depending on the workflow you are using, change exposure parameters either in Corona VFB’s “ColorMap” tab, current camera settings or in Render Setup > Scene > Camera/Exposure/Tone Mapping.

Wrong lighting
Make sure you are using proper light units and intensity and that your lights are facing the right direction. 

Wrong materials
Make sure your materials are not too bright or too dark.

Source: coronarenderer.freshdesk.com