With photography, one perversion can segue to another. Voyeurism focuses such attention on where the photographer could possibly have been placed, or what they could have been doing at the moment of surreptitious capture that in the very attempt to achieve transparency, the agent becomes the essence of the image. It is precisely through efforts to become invisible that the person behind the camera takes center stage. Thus voyeurism begets a certain narcissism.

Two new shows that dramatize the photographer as absent presence in images of candor and intrusiveness open this week: Jessica Craig-Martin’s “American Summer” at Greenberg Van Doren Gallery is the first New York show of this internationally fêted society photographer (she works at Vogue and Vanity Fair) since her 2001 exhibition at P.S.1. Kohei Yoshiyuki, by contrast, has remained invisible for a quarter of a century. “The Park” at Yossi Milo Gallery, a body of work from the 1970s documenting casual sexual encounters in three Tokyo public parks, was shot at night using infrared-sensitive film and filtered flashbulbs. This work is being shown for the first time since 1980, and marks the artist’s American debut.

Their prints constitute an essay in contrast — hers, in gaudily opulent color, are Where Ms. Craig-Martin has made the moneyed Hamptons social circuit her locus, Mr. Yoshiyuki’s subject is a sexual underclass, whether self-selected or forced toward social margins.

What unites these artists — despite such distinct production values — is the way each documents a specific, historical, and peculiar — yet in some ways ubiqutious — scene. Like Dante or Boccaccio, it is through attention to particulars of time and place that they are able to conjure vices that transcend them.

In Ms. Craig-Martin’s work, drastic cropping is a defining characteristic. Image after image amputates or decapitates her revelers, homing in on torsos, legs or feet, or a snatch of mouth. In each case, the viewer’s mind oscillates between possibilities of what this strategy means as violently as the eye seems to tip and lurch around the party. Sometimes, for instance, there is the kind of exactitude of an anthropological specimen: “Cancer Benefit, Southampton 2006 (Brooks Brothers Weiner)” (2007) links the sewn logo on a waiter’s pink T-shirt to the last remaining canapé on a tray of grass. Other times, it is more as if to say, “This is what I could get away with.” The cropping is highly functional, homing in on the only details that matter, sparing individualizing features that would distract.

With “Cancer Benefit, Southampton 2006 (Real Wasps)” (2007), however, in which the lower halves of a poolside couple — he in chinos and a blue blazer, she in a cocktail dress and waxed, bronzed legs — are shown, the intentions behind the cropping are more ambiguous. The image might be saying that half tells all — that their individuality is superfluous. Or it might be saying that the grounded, animal side of their personae are more apropos to the party mode than their higher selves. Or perhaps the cropping conveys coyness about identifying individuals, introducing an element offear or awe toward the satirical victims.

The best images, such as “Cancer Benefit, Southampton 2006 (Air Kiss)” (2007), in which the smooched face belongs uniquely to a named individual, Ms. Denise Rich, instill ambivalence about whether the photographer is a skilled paparazzo or was herself as happy-go-lucky partygoer who made sense the next morning of what her wayward camera cropped. Whether or not this is true, the images imbue this sense of nonchalance. The focus is crystalline and the printing pristine, but vertigo can imply a drunken lense.

The less successful images are ones where there is no sense of speed or intrusion. In “Real Estate Brokers, Southampton 2007 (Peace / Cannabis Loafers)” (2007), for instance, the shoes, each embroidered with an instantly recognizable sign, seem worn to have been photographed. Whereas “Watermill Center Benefit Gala 2007 (Town Car to Tent)” (2007), in which a pocketbook swings aimlessly by its wearer’s thin, muscular legs, is a stolen moment, a gesture caught between expectation and tedium, a quiet, subtle image.

The cumulative effect of Ms. Craig-Martin’s merciless cropping, sumptuous color, emphatic scale, and pristine focus is, despite its power and clarity, to add another layer of ambiguity to her work, this time between visceralness and artifice.

The odd angles, a sense of snapshots taken on the sly, the fragmented body parts, make the action seem present tense, unmediated, all the more real. Flesh is captured in ruthless precision: Too much information outbids too much money to emphasize that even the rich have sweaty pores, scars that can’t be disguised, bodies that age. But the photography takes dancing, posing, dolled-up bodies in another direction: toward flattened-out, abstracted shapes, colors, and textures.

Mr. Yoshiyuki’s nocturnal forays culls both homosexual and heterosexual activity in three Tokyo parks, with straight couples his focus in the early 1970s, gays in 1979. It could be argued, however, in view of the crucial role played by onlookers, that the sexuality in both instances is pansexual — that the where of sex is more important than the with whom.

Sometimes the viewer senses people turning around and acknowledging the camera, perhaps as the filtered flash from a previous image captures their attention. But even without evidence that lovers are literally posing for a camera, there seems little point in describing the relations depicted in terms of intimacy. Often the onlookers are as much the subject as the primary participants; their stalking of the couples entails more bodily energy than those furtively engaged in actual intercourse.

The thrill and squalor of these images reflects far more on the act of taking them than the actions captured. The lovers are bizarrely coy, remaining mostly dressed and opting for the simplest erotic transactions. The crucial ambiguity in Mr. Yoshiyuki’s work isn’t in his subjects’ libidos but his own. Who is out there behind the camera each night: an anthropologist, an artist, a sexual deviant, a free love advocate, a blackmailer?

The grainy, soft texture of the images, meanwhile, has more to do with the constraints of surreptitious night photography than with aesthetic intentions, but the result is a strangely wistful fusion of prurience and poignancy.

“Jessica Craig-Martin: American Summer” until October 6 (750 Fifth Ave. at 57th Street, 212-445-0444).

“Kohei Yoshiyuki: The Park” until October 20 (525 W. 25th St., between Tenth and Eleventh avenues, 212-414-0370).