Lightening up an underexposed image, method 3
This time, let’s use a Curves adjustment layer to lighten our image. Open the image and in the Adjustments panel, click on the Curves icon. Now select the little hand with the double-facing arrow at the top left of the Curves Adjustment panel and click-and-drag inside the image to adjust the curve. Move the cursor over the image and click on the area of the image you want to brighten. While holding down the button, move the mouse up. This will adjust the curve and lighten the image.