Ever since Pakistan bowlers showed the potential of Reverse swing, it has been a huge area of interest with cricketers and commentators alike.
However, there is a difference between reverse swing(when ball moves differently in the air) and contrast swing (when it moves differently due to surface differences).
Rabi Mehta and Garfield Robinson explain the differences:
Often confused with reverse swing is what is properly known as contrast swing. How is it different from reverse? Contrast swing occurs when the ball is released with the seam straight up, rather than angled towards slip or leg slip. The ball will swing when there is a contrast in surface conditions between the two sides of the ball. The greater the disparity in roughness and smoothness, the greater the inclination for the ball to change direction. At the bowling speeds normally achieved by fast bowlers, say between 70 and 85mph, the ball will swing towards the smooth or shiny side.
Indian fast bowler Mohammed Shami consistently bowls with the seam straight up (contrast mode), and normally operates at speeds of up to 85mph (close to 140kph). ESPNcricinfo’s match report from Shami’s Test debut, against West Indies in 2013, says: “Shami bowled consistently in the late 130s on a slow pitch, and was a different proposition with the ball scuffed up, finding movement that had not been there for him with the new one.”
The movement was noticeable only when Shami returned to the attack in the 42nd over. Unsurprisingly, it was referred to as reverse rather than contrast swing at the time.
So are there any advantages of contrast swing over reverse swing?
One, it is much easier for non-swing bowlers to release the ball with the seam straight up rather than angled. Contrast swing is also possible with the seam completely bashed in – a common occurrence in the subcontinent. A prominent seam plays a critical role in conventional and reverse swing. Whenever the old ball swings, it is immediately said to be reversing. Contrast swing is rarely mentioned, and yet, that is more likely the correct characterisation. What we have seen, more often than not, is that both contrast and reverse swing are lumped together and labelled reverse.