If the shutter closed too soon, underexposure took place and the line was black.
From the en.wikipedia.org
So he may suffer from underexposure for now, but that won't last much longer.
From the usatoday.com
Usually sunrises and sunsets can be made a little richer in color with a slight underexposure.
From the ocregister.com
It's a shame Pentax suffer the injustice of underexposure.
From the guardian.co.uk
Ruzicka is another case of underexposure.
From the usatoday.com
The heroine, Catherine Keener's Kate, suffers from a surfeit of empathy, but the movie has suffered only from underexposure.
From the online.wsj.com
At best, a flat card is an approximation to a three-dimensional scene, and measurement of a test card may lead to underexposure unless adjustment is made.
From the en.wikipedia.org
Digital capture tends to be more tolerant of underexposure, allowing better recovery of shadow detail, than same-ISO negative print film.
From the en.wikipedia.org
Factors considered may include unusual lighting distribution, variations within a camera system, filters, non-standard processing, or intended underexposure or overexposure.
From the en.wikipedia.org
More examples
The act of exposing film to too little light or for too short a time
Inadequate publicity
In photography, exposure is the total amount of light allowed to fall on the photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance over a specified area.
Underexposure is a 2005 Iraqi film, in the docufiction style, written and directed by Oday Rasheed, produced by Enlil Film and Arts. ...
(Underexposed) Exposing photographic material to too little light, because the image is too dim or exposure time is too short. Results in insufficient density and shadow detail in final image.
(Underexposed) A usually undesirable situation whereby a camera's digital image sensor or film was exposed to insufficient light under the prevailing conditions (i.e. based on the prevailing light and the camera's exposure settings). ...
(underexposed) film or emulsion that has been exposed for less than the recommended time, or at full time with a weak light source, or with a light source that is positioned too far away.
When not enough light is allowed to affect the image , creating a dark and dull image
A condition in which too little light reaches the film, producing a thin negative, a dark slide, or a muddy-looking print.