Tuesday, 2 June 2015

Spade wings

InsectorodI haven't had a photo of one of these for a while (pic right). It's a picture, taken recently, of a hovering insect, probably a hoverfly. The view with the naked eye didn't look like this photo. It is what I call an insectorod. It's doesn't resemble a typical flying rod but neither is it an accurate representation of the insect being photographed. The insect did not have those unusual-looking wings. Anyone trying to identify the insect from this photo might decide that it is apparently an unknown species!

The problem is that the wings are motion-blurred but give the superficial appearance that they are not. Hoverflies have a wingbeat rate of around 120 per second. This exposure had a shutter speed of 1/250s. So while the shutter was open the wing moved half a wingbeat, either one up or one downstroke. And so we see the full down or upward motion of a wing, as if it was a solid object, givng rise to the spade-like shape.

Motion-blur is not always obvious in photos, especially if it only applies to one object in the scene. It can lead to odd-looking objects which are not as they seem! It is something to consider when examining an anomalous photo of something oddly-shaped.

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