Do you mean "lens hood"?
An improperly narrow lens hood would cause a dark ring around the edges of the photo. If the hood has "leaves" or "petals" it could have dim spots in irregular places.
Is this a Canon lens? If so, are these the correct Canon lens hoods for the particular lens? If you have a mis-matched lens and lens hood, that might be an issue?
But another issue could be unflattering shadows from on-camera direct flash? One's oen nose or forehead will cast ugly shadows on a subject's face. You probably already know this, but if you bounce your flash off the ceiling or a neutral wall, then it decreases these shadows a lot.
Also helpful is the use of a reflector. You can pay $60.00 for a collapsible reflector, or you can get the same one on Ebay (Chinese) for like $10.00) Position the reflector to cast bounced flashor reflected sunlight up onto the subject and you are good to go.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.