During World War I, ships were painted in zebra stripes to deceive the enemy. The effectiveness of this “dazzle” camouflage was never quite clear, but a new study suggests that these zigzag patterns can be quite deceptive when they move.
USS West Mahomet painted in “dazzle” camouflage. (Image: US Navy)
Empress of Russia painted in “dazzle” camouflage (Image: UBC)
Dazzle camouflage was invented by British marine artist Norman Wilkinson. The idea wasn’t to conceal a ship, but to trick enemy combatants. Ships painted in these zigzag patterns were difficult to discern, making it difficult for the enemy to estimate a target’s range, speed and heading.
Dazzle camouflage was adopted by both the US and British Navy. Each ship featured a different pattern to avoid classes of ships being recognisable to the enemy. Evidence for the success of dazzle was mixed, and the funky looking strategy was eventually phased out (though some ships retained these patterns well into World War II). Today, the technique is considered antiquated.
A new study published in PLOS One has finally shed light on what, exactly, makes the dazzle strategy work. As it turns out, to make dazzle really effective, it can’t be static — it has to move. Researcher Joanna Hall, who works out of CamoLab at the University of Bristol, performed a set of experiments that showed how moving patterns can twist and warp our perception of an object’s speed.
Using computer-based visuals, Hall and her colleagues sought to understand how the perceived speed of a target is affected by the addition of a moving pattern. Their research shows that when a pattern on a target moves in the same direction as the target, the target appears to move faster. And when the pattern moves in the opposite direction to the target, it appears to move more slowly. The effect essentially causes an optical illusion.
For an object the size of a Land Rover, that equates to a targeting error of up to 2m at a distance of 70m when the vehicle moves at 90km/h. At its maximum effect, the perceived speed was increased or decreased by around 15 per cent, and the effect also appeared to be robust under stressful conditions.
An example of the experimental conditions. The white arrows indicate direction of target and the red arrows indicate direction of dynamic texture motion. The red rectangle indicates the proportion of the texture that is moving, and the remainder of the texture is static. (Image: JR Hall et al., 2016)
“Our research is the first to quantify the effects of a moving pattern on a moving target,” Hall told Gizmodo. “We showed that a moving stripe pattern can increase or decrease the perceived speed of a moving target in a reliable and predictable manner.”
The dazzle doesn’t have to appear across the entire vehicle or target. The researchers discovered that the perceived speed of a target can still be distorted with only a small patch of the dynamic dazzle at each end.
The researchers didn’t test their hypothesis on actual Land Rovers (or ships for that matter), but the same principle is likely to apply. “If technology were available to construct a surface able to display a moving pattern,” Hall said, “in theory it could be applied to any object for which it would be useful to disguise the speed.”
Hall said that one potential military application would be on vehicles that are at risk of attack from rocket-propelled grenades, as the distortion in speed perception could result in a targeting error, thus reducing the risk of a direct hit.
Looking ahead, the researchers would like to take these findings and test the effect in real world conditions. Should it work, we might see a return of dazzle camouflage, though in its modern, dynamic form.