Underexposed means too dark because too little light was let in. An underexposed shot, badly underexposed, underexposed film.
In digital photography it is the safer error, because detail can be pulled back out of shadows but a blown-out white holds nothing to recover. With film the reverse is true, which is why photographers who learned on film still expose differently.
1adjectiveunderexposedToo dark because too little light was let in.
“The photos from the concert were underexposed, and you could hardly see the band.”
underexposed is a fault.
underexpose comes from under- + expose.
Etymology from Wiktionary, CC BY-SA