Over and under exposure with flash
The reverse process also works when I get over-exposed photo. The first thing I do is get away a little of the person. If I can not get away or is getting too much light photo flash, then change the EV to the scene is less illuminated by the flash (EV negative).
And if the photo is still overexposed, then change the ISO to a lower ISO (ISO 400 to ISO 200 for example).
In the next pictures we will see how to get the flash away from the model, it comes out increasingly dark. The first photo is well exposed. And in the 2 photos below I walk away more and more.
Another resource that can be used when the picture comes on exposed is to use a piece of white paper or natural color semi transparent and put it in front of the flash.
This will remove power to the flash as less light will pass through the paper.
It also serves as a diffuser and it will make the light soft, diffuse, shadows will be less dark and hard. It would be like using a light box in a studio flash or external.