(1) Expose to too little light
(2) Expose insufficiently
(1) What you should be seeing is; if you overexpose the image should be lighter and if you underexpose the image will be darker.
(2) Since snow is so reflective, it can force the camera to underexpose the darker, less reflective subject in your scene.
(3) If you're using a camcorder lock off the white balance, add a blue filter and underexpose the shot.
(4) From an imaging perspective, several photographs were either underexposed or blurred due to insufficient exposure time.
(5) The left image is underexposed , resulting in a dark image: foreground detail is heavily muted, and the window to our right is completely invisible.
(6) Keep the sun itself out of the frame or it will trick the meter into severe underexposure .
(7) In the case of underexposure or overexposure, the photograph could immediately be taken again.