If you captured a hard-to-see, semi-transparent specter or demon on a low-quality camera, you can make it stand out more by applying a cross-hatch filter to the video or photograph using software such as Final Cut Pro or Photoshop.
The effectiveness of the cross-hatch filter, when applied to a specter, is illustrated in the newer version of Spectre of Demon Illuminated by Light; compare it to the original to see just how much it helps.
