ZipGrade can accommodate a wide range of lighting conditions, including most shadows. For the best scanning speed and accuracy, pay attention to the lighting environment. Issues with scanning consistency are most often related to the lighting conditions.
Diffused or reflected light is best. Try to avoid direct or task lighting shining directly on the answer sheet.
Stay away from desk lamps.
Bright or direct lighting can cause glare on the paper. Since pencil marks are made of graphite, this glare can cause them to appear white rather than dark. The app includes logic to identify these issues. But it does affect the margin of accuracy as the app can only 'see' what the camera captures.
You may receive a message during the scanning that there is glare on the answer sheet. If you receive this message, move to a different part of your desk or angle the lighting away from the paper.
Often, slightly reducing the lighting will improve scanning.