Sony alpha HVL-MT24AM Mode D'emploi page 53

Note
If a close-up subject is illuminated from the side using an arm, strong shadows may
occur. Strong flash illumination from behind the subject can cause flaring.
 This condition is particularly likely to occur with a 50mm F2.8 Macro lens with
flashtubes mounted on arms.
Example:
With arms from the sides
Without arms from the front