Corn is ready to be picked as soon as the ears have completely filled out. This goes for sweet corn and roasting ears.You can tell when this happens by feeling the end of an ear. If it's rounded or blunt rather than pointed, the ears are ready. The silks also dry up when the ears are almost ready to be picked.
The picture may be of blunt corn - ready for harvesting
see https://garden.org/learn/articles/view/794/Harvesting-Corn/
The next question is Why is "BLUNT" capitalised in the drop?