Like gooseberries, currants are still banned in some states and counties due to white pine blister rust concerns. The currants in the photos are grown in northern Pennsylvania where they ripen with blueberries, and serve as good additional mid-summer berries following the wave of spring and early summer berries.
Black currants are mid size between gooseberries and red (and white and pink) currants. All of these ribes species can range from minimally tart to very tart. In my experience, red currants have been among the most tart. They make a very good jelly and are also enjoyable as fresh eating in small amounts, the sweeter the variety the better. Considerably smaller than blueberry size.
Black currants can be very tart too or have more of a sweet grape pulp flavor with a smoky or musky finish. Black currants have more of a smooth jelly grape pulp texture and thinner skin than a gooseberry, with a small to very small blueberry size.