What it means
Most low-cost cameras use a rolling shutter, which exposes and reads the sensor one row at a time. If the vehicle moves while the rows are read, the top and bottom of the plate are captured at different moments and the characters lean or stretch. A global shutter avoids this because the whole frame is captured at once.
The effect grows with speed. A vehicle at 100 km/h moves about 2.8 cm every millisecond. Over a readout time of several milliseconds, that movement is large compared with the stroke width of a plate character.
How it applies in India
Indian highways carry very fast cars next to slow trucks and two-wheelers, and expressway enforcement must read plates at the top of that range. For highway ANPR and speed enforcement, specify a global shutter sensor, a short exposure and matched IR illumination. For a slow society gate, a rolling shutter can be adequate. The Recon Global Shutter Camera is Stellarview's highway ANPR camera.