Individuals are also sometimes abbreviated when referred to in writing, so a dominant person may be referred to as a Dom for milf fuck a man, and a Domme for a woman. 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. Double Stuffed , Double Vaginal , or Double Anal pornography involves the penetration of one orifice by two penises or other objects. Transgender pornography features performers who cross-dress for sexual gratification, either for themselves or for their partners. Pornography is often distinguished from erotica, which consists of the portrayal of sexuality gay sex video with high-art aspirations, focusing also on feelings and emotions, while pornography involves the depiction of acts in a sensational manner, with the entire focus on the physical act, so as to arouse quick intense reactions. Normal quantities of ejaculate range from 1.5 to 5.0 milliliters hentai porn . The reverse of this, in which nude women interact with clothed men, is called Clothed male, naked female . It is used, for example, at fertility clinics to stimulate sperm donors. The buttocks in human females thus contain more adipose tissue than in males, especially after puberty. Facial cum shots are currently regularly portrayed in pornographic films and videos, often as a way to close a scene. Terminology for roles varies widely within the various BDSM subcultures. A variant of A2M is ATOM where a performer inserts his penis directly from one recipient anus into a second recipient mouth. A female dominant in a master/slave relationship is often termed a Mistress, not to be confused with the colloquial usage of mistress as a kept sexual partner without a similarly formalized power relationship. Emetophilia pornography involving vomiting and gagging. Some BDSM practitioners prefer a code of behavior that differs from SSC and is described as risk aware consensual kink , indicating a preference for a style in which the individual responsibility of the involved parties is emphasized more strongly, with each participant being responsible for his or her own well-being.