
Nan Goldin's photographic portraits both depict and exude intimacy.
Her subjects are friends and close acquaintances, and for Goldin, every event in their lives is equally worthy of being documented.
This fact is made abundantly clear by a glance at some of her images' titles:
Roommate in her chair, Boston, 1972; David and Bruce after sex, Provincetown, 1975; Bobby masturbating, NYC 1980; Suzanne on the bidet, New Jersey, 1983; Brian on the phone, NYC, 1981; Self-portrait with Brian having sex, NYC, 1983
Pictures as apparently mundane as a seated roommate find themselves side by side with photographs of sex or masturbation, yet whatever the subject, all receive the same empathetic and unsensational treatment.
The fact that Goldin is granted such close access to those around her is testament to the strength of her relationships, yet she frequently turns the camera on herself with the same unflinching honesty and directness.
Like Koons, she has photographed intimate aspects of her own sexual relationships - Self-portrait with Brian having sex; Nan and Brian in Bed - but her evocation of such moments could hardly be more different to Koons' glitzy, self-conscious productions.
Despite the uncompromising nature of her work, Goldin's photography has generally avoided major controversy.
This is partly due to its documentary aspect, in which sex is just one of the multiple realities she strives to represent. To emphasise this, her photographs are generally exhibited in large groups that provide a balanced and complete view of her subjects.
Nevertheless, a 2007 exhibition in the UK of her 'Thanksgiving' series became the focus of a police enquiry regarding a specific image, Klara and Edda belly-dancing.
Depicting two young children dancing, one is lying naked on the floor, legs apart.
The photograph was seized by police over concerns that it was 'indecent', and although later cleared of charges, the entire show was pulled by the collection's owner in protest.
Such images, however innocent the context in which they were made, have clearly become a principal focus of modern censorship.
German photographer Thomas Ruff is best known for coolly objective images which support his claim that "photography can only reproduce the surface of things".
Ruff records, but generally refrains from implying a particular viewpoint, inviting others to supply their own interpretation of his work.
With the Nudes series, Ruff is specifically interested in just how far he can restrict immediate sexual association while still leaving the subject matter clear.
His aim, in other words, is to render sexual material somehow un-sexual, and to achieve this he employs a number of distancing devices.
The sources for his works were downloaded from the internet, re-photographed, then blurred.
The loss of focus invites comparison with Gerhard Richter, whose own use of the blur in his highly realistic 'photo-paintings' provides the sole indication that they are emphatically 'portraits of photographs'.
In similar fashion, Ruff's images are photographs of photographs from which he wishes to remove his own interpretative presence.
To this end, the only information he specifically provides regarding their content is a single word: 'Nudes'. Other than this, viewer are left to draw their own conclusions.
Our inability to make out exactly what is happening may cause us to lose interest or even experience frustation. Eventual recognition of the context might cause concern, shock or even a voyeuristic sense of pleasure. For others, the partially veiled nature of the images could render them more erotic.
Yet as Ruff has made clear:
'what people see, eventually, is only what's already inside them.'
In a close parallel to Wim Delvoye's X-ray series, if these images are to be termed pornographic, explicit detail is supplied solely by the viewer. The final interpretation comes from within.
The bondage that features so predominantly in Nobuyoshi Araki's photography has several precedents within Japanese art, in particular Shunga, the erotic art of the Edo period (1603 - 1867).
Often created by highly regarded artists and widely enjoyed by men and women at all levels of society, Shunga cannot be aligned with western notions of pornography.
While Araki's photographs tap substantially into this historic genre, his erotic imagery often incorporates the stylistic influences of modern Japan - popular culture, fashion photography and the thriving sexual sub-culture of Tokyo in which erotic bondage (shibari, kinbaku) is considered a highly subtle art form.
It is sometimes overlooked that many other forms of traditional Japanese art and culture are of interest to Arakai. Ikebana, or flower arrangement, is a particular favourite, and his obsessive documentation of its systematic, highly formal aesthetic provides an unlikely though important parallel to his studies of erotic shibari.
Nevertheless, the fact that Araki's work is rooted in very specific contexts does not negate its often controversial nature.

His erotic photographs of bound women inevitably provoke associations of captivity, slavery and sexual objectification. Although many viewers find this highly disturbing it is, of course, precisely these impliications that render such scenarios erotic for others.
Perhaps ironically, Araki's photographs have been subject to censure more often in Japan than the West, with obscenity charges brought against the artist in 1992, and the arrest the following year of a gallery owner.
The basis for such action was not the images' context, however, but their depiction of pubic hair; a long-standing - and to Western audiences, unusual - Japanese prohibition that was eventually overturned.
The situation reminds us that definitions of the sexual - and, indeed, sexually perverse - are highly subject to social, political and historical influence. Araki's erotic photographs have always ignited controversy, but for very different reasons from different viewpoints.
Limited editions by Nobuyoshi Araki >
Dumas' work focuses on the momentous realities of life such as motherhood, birth, death and, of course, sex.
While Dumas' paintings have often depicted women (and, more rarely, men) in suggestive poses, the sexual act itself - either as solitary masturbation or with a partner - is rarely presented in detail.
While sex is certainly an important theme in Dumas' work, nudity itself is almost of greater concern:
"The public display of nudity ... as well as the reasons given to justify or banish it... has always been one of my main artistic interests.
The traditional (male) painter uses it to promote higher aesthetic values ... the porn industry to promote masturbation, while film stars only do it if it's part of the story. Most people don't do it at all."
Dumas has made it clear that, whether the subjects of her paintings are clothed or not, her work is about "stripping people" to essential, emblematic states where "... surnames disappear and first names are fictional."
If, through nudity, people reveal themselves physically to the world, sexual impulses are similarly raw and undisguised, providing rare insight into the 'truth' of an individual.
Dumas' reluctance to focus explicitly on intercourse itself is not evasive; her principal interest lies in individual rather than shared emotional states, with exhibitionism, nudity, masturbation or the implication of coitus lying at the heart of her artistic approach to sex.
Limited editions by Marlene Dumas >
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