I’ve seen every cut of Ridley Scott’s Blade Runner, and yet when I watched his new-absolutely-last-I-promise director’s cut, I’d never felt so pierced by the importance of photographs in the movie. The Terrell Corporation manufactures Replicants (humanoids with a four-year life span) and supplies them with personal photographs — Mom, Dad, the dog, the house and its piano — so that they’ll believe they have a real past. The photos give them a human back-story. Most of the photographs in this hallucinatory color film, though, are black and white, and humans aren’t, so in a sense these “memories” are already falsifications or simulacra of the past, just as the Replicants are simulacra of human beings. I’ve spent so much of my life looking at and thinking about photography of all kinds — daguerreotype, tintype, digital, radiographic; straight, formalist, vernacular, mystical — that I feel pretty toughened about the affects photographs so effortlessly express, so Blade Runner’s memory conceit shouldn’t have hit me so hard. And yet when I now look at portraits, I feel as never before a biting sensation of loss, or loss’s impending-ness, no matter if it’s an album snapshot of wedding debauchees, a tintype of a live Civil War recruit, an excruciating yearbook pose, or a Chloë Sevigny glam shot. What I see are perishables, already on their way toward the other side, wherever that may be. For all the tactile illusion of sensuous presence that photography smuggles into consciousness, it also brings the ghost inside the flesh, the body’s breath that sooner or later goes.

I know this has to do with how an image transcends its own appearances and that the template of personal history shapes our response to images. The inglenook of an exhibition currently at the Museum of Photographic Arts, Picturing the Process: Portraiture Through the Lens, contains only a couple dozen pictures yet offers one meditative occasion after another on the nature of life and memory, or memory in life, how we prepare to remember ourselves with a representational device whose mechanics, unlike those of painting or sculpture, are master-able by any old fool. Digitization has made portraiture an even more voracious and omnipresent retrieval system. The most exhaustive visual archive of troops at war is right now being created thanks to cell-phone cameras. A portrait is inevitably some kind of memento mori, whether — to cite examples from the exhibition — it’s a daguerreotype of a dog seated on a chair, a tintype of a teenager about to go off to the slaughter fields of Antietam or Gettysburg, a photographer’s self-portrait (invariably fragmented or only a shadow), or a raucous celebrity image of Janis Joplin. How tender-tough she looks, pointing straight at us, wearing that sweet, dizzy, welcome-to-the-piece-of-my-heart smile.

These are included in a show, billed as a simple sampling, that’s really a teacup history of portraiture, from Daguerre’s 1839 invention, which proliferated recklessly because of the expanding middle class and would within 20 years include, among other genres, dirty pictures (not included in the show) now valued by collectors of erotica, then on to the earliest paper photographs made by Henry Fox Talbot and misted, late 19th-century Pictorialism (represented by a mightily depressed Alfred Lord Tennyson), up to Larry Fink’s gleaming 1957 portrait of a portrait: an artist’s model sits dressed and splayed on the floor of a painter’s studio, her dirty feet-bottoms reminiscent of Manet’s Olympia, and on the wall behind her hangs the painter’s triple portrait of her in the same pose and outfit.

Photographers make light into an occasion for excitability. “I have forced the sun to take pictures for me,” Daguerre exclaimed. “[I have] seized the fleeting light.” The other fleeting thing is us, and the fleetingness has its comic turns, as in a picture that made me laugh out loud: Untitled (Knife Thrower Signor Arcaris and Sister Rose?). Flashy in his gaucho get-up, said Signor A. poses proudly next to his sister, poor kid, her chiffon-ruffled, unnaturally pinched hourglass figure fastened to a rotating wheel, outlined by hungry looking knives. When Daguerre was patenting his one-off, metal plate process, Fox Talbot, also in 1839, was patenting his Calotype process that would rule the day, because he figured out how to make negatives that yielded multiple prints. The machine Talbot boasted could produce “evidence of a novel kind” was soon being used by detective squads to record crime scenes and register criminals. Picturing the Process includes a 1910 mugshot of one Thomas Wallace. Like most portraits, it inventories its subject, but in a literalist, depersonalized way: the information card presents profile and frontal views and vital stats (“HAIR: med-chest.; Complexion: ruddy; Weight: 142”) but says nothing of his purported malfeasance, depriving the representation of any moral quality. He might as well be that other popular photographic subject: sleep’s simulacrum, death. Nadar, pseudonym of Gaspard-Félix Tournachon, made portraits of every famous personage of Second Empire Paris — Baudelaire, Delacroix, Ingres, himself. His picture of the dead Victor Hugo in bed in no way makes the titan look diminished. The great leveler seems to have flattened but not leveled him. Fox Talbot himself made a death portrait of Nicolas Hennem, his assistant in creating all that evidence of a novel kind.

Photography became a representational activity available to anyone who by 1882 could afford one of George Eastman’s cheap Kodaks, a Brownie prototype that contained a roll of 100 paper negatives. Soon the masses, in love with unscrolling narrative portraiture, were packing motion picture theaters all day every day during the Great Depression. In the worst of times, that fame-making industry thrived. As for the Brownie and still photography, even nobodies now had a new self-celebrating device. With stupefying alacrity, the camera created in us the ability to fabricate a second self, a camera-ready self that most of us can present on command. Photographers of course know how to exploit that self-awareness and projection. Bruce Davidson’s portrait of a teenage couple on New York’s East 100th Street is nearly rent apart with ambiguity: a beautiful young girl full of hope and promise smiles into the lens; the boy, noncommittal, slightly wary, observes his (presumed) sweetheart from a cautious distance. If that’s an image of unequivocal equivocation, James Fee’s portrait of David Lynch is a refractory homage to the film director’s own distorting, horror-ride chromatics. It’s a picture about warped, delusional, smeared self-perception. Lynch appears as a color-warped figure trapped in a swirling, smudged, corroded nimbus. He looks trapped either in the process of coming into being or passing from it.

Picturing the Process: Portraiture Through the Lens is on view at the Museum of Photographic Arts until July 6.