Jerk off instruction features a performer encouraging or instructing the viewer to masturbate, often culminating in a countdown at the end of which the viewer is invited to induce orgasm. Both forms of pornography generally contains nudity. Lying face down on a comfortable surface such as a mattress or pillow, the penis can be rubbed against it. Many fantasies include the macrophile shrinking before a normal sized woman or keeping his or her normal height while the partner grows in size. There has been an increase in discussion and portrayal of masturbation in art, milf xxx popular music, television, films, and literature. Normal quantities of ejaculate range from 1.5 to 5.0 milliliters . The porn industry and gay boy porn viewing public were shocked by the then-taboo hentai porn spectacle of a white woman having sex with a black man. Such explicit sexual interaction is seen only rarely in public play spaces, and it is sometimes specifically banned by the rules of a party or playspace. Shibari is a Japanese word that literally means to tie or to bind. Rape pornography features performers simulating rape. For much of the history of cinema and television, lesbianism was considered taboo, though since the 1960s it has increasingly become a genre in its own right. For instance, Amateur Allure has a trademark shot where the sexually performing cameraman circles a handycam around the sexually performing model head. John Stagliano is considered to have started the gonzo pornography genre with his Buttman series of films. Common positions include lying on back or face down, sitting, squatting, kneeling or standing. The work of Bruce Seven has been called reality porn, due to his lack of using scripts and asking his performers to act naturally in their own character. It is used, for example, at fertility clinics to stimulate sperm donors. They further argue that setting a discrete line between safe and not-safe activities ideologically denies consenting adults the right to evaluate risks vs rewards for themselves; that some adults will be drawn to certain activities regardless of the risk; and that BDSM play—particularly higher-risk play or edgeplay—should be treated with the same regard as extreme sports, with both respect and the demand that practitioners educate themselves and practice the higher-risk activities to decrease risk.