(faster shutter speed / less light). Aperture (or f-stop) refers to the size of the opening in the lens of the camera when a picture is taken. As you are focusing the camera, the lens is wide open with the largest aperture supported by your lens.
The harvest season typically falls between August & October in the Northern Hemisphere and February & April in the Southern Hemisphere. With various climate conditions, grape varieties, and wine styles the harvesting of grapes could happen in every month of the calendar year somewhere in the world. In the New World it is often referred to as the crush.
Sweetness. Grapes become sweeter and less acidic as they mature, which is the most important factor in determining if grapes are ripe. The sweetness of the grapes also depends on the cultivar planted and growing conditions. Sometimes, a cluster of grapes will ripen unevenly.