rod artefact of video camera

'Rods': Artefacts of Moving Picture Technology

Just a brief note on 'rods', promoted in the late 1990s as 'paranormal' objects, generally out-of-focus lines with a regular pattern, found on video images.

Every observational device produces artefacts: coloured diffraction with lenses, Newton's rings with thin films, an eyelash seen in an eyepiece, stretched-out (or compressed) moving objects with cameras that have focal-plane shutters, and the appearance of double lines in a single membrane with electron microscopy are examples in ascending order of likelihood of a mistake.

Insect wings come in several designs; 100 to 600 beats per second are common with flies, mosquitoes, and midges; the smaller the faster, generally. A video camera operating at 30 frames per second, each frame taking (say) 1/100 of a second, will record six beats of an insect with 600 beats per second, run together on the same frame. In fact the number of wing-beats per second can be calculated from such videos. Butterflies and moths have much slower wingbeat rates which don't show as 'rods'; probably this is the reason for the uninteresting colouring of 'rods' generally.

Insects aren't generally well-lit, so good videos of 'rods' usually have a dark background, the camcorder itself happening to be brightly-lit by sunlight or a night security camera. (Or they may be dark against a bright sky). Because of the insect connection, these images are often made at dusk and in country areas. Obviously the camcorder focusing is usually on mid- or far-distant subject-matter, giving the impression of fast speeds.


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HTML Rae West First uploaded 2013-Jan-21 'Rod' image from a Youtube by HSWT2009