Over Dean Kessmann’s 30-year career, photography has changed dramatically, and the D.C. artist seems to have thought deeply about every shift. His impressively diverse VisArts retrospective, “Light Years, Chemical Days, and Digital Seconds,” includes traditional film prints, negative-less photograms and images generated by computer programs and digital scanners. The results are rigorous, but also playful.

Kessmann, who has taught at George Washington University since 2002, often trains his lens on examples of found abstraction. This survey begins with black-and-white 1994 shots of St. Louis construction sites, which emphasize patterns but are clearly recognizable as pictures of the real world. Later, he made color pictures in a similar mode, but more tightly focused so that they can serve as pure exercises in color and form.

Recently, the photographer has devised mysterious, but sometimes decipherable, images of squished plastic bags and details of food packages. The plastic bags appear organic and oddly sensuous. The food packages feature massively enlarged decorative elements, badly aligned printing and the texture of cardboard itself to yield what the artist terms “Utilitarian Abstraction.”

Where Kessmann often depicts things that are visible but rarely noticed, he also uses computer imaging to produce pictures only a machine could allow anyone to see. “A Year at a Glance” superimposes the covers of multiple issues of art and photography magazines to condense the publications’ 2007 runs into a single, humanly impossible glimpse.

That’s just one of Kessmann’s series, whether chemical or digital, keyed to years, days and seconds. Whether the photographer is shooting on the street or arraying gray test strips to suggest stripe paintings drained of color, he’s chronicling the passage of time. Technology can change suddenly and unexpectedly, but clocks tick at a steady pace.

A former photo editor at National Geographic, Chris Combs takes some of his cues from digital photography. But the D.C. artist is more interested in interactive and time-based electronic systems, as he demonstrates in his VisArts show, “Lossiness.” (The title refers to the technique for compressing digital information so that it requires less storage space but remains intelligible.)

One of his Comb’s fundamental concerns is electronic surveillance, reflected in “Impressions,” a machine he made to respond to a nearby person’s movements with green LEDs that twinkle on a round, black field. The effect is benign, even pretty, but the implications less so. A machine that can watch people can, potentially, control them.

Downstairs at VisArts, Sue Wrbican’s “This Iridescent Era” begins with a 1990 work by other artists: “Oil Tanker” is a relief sculpture of a ship assembled with black-painted consumer-grade plastic objects, assembled by the Northern Virginia artist’s late brother, Matt Wrbican, with the sea and sky rendered by Phil Rostek and James Nelson. Also included is a large painting newly made in response to “Oil Tanker” by Claire McConaughy, a longtime friend of Matt Wrbican.

Sue Wrbican’s contributions to the show consist mostly of near-abstract prints whose shapes suggest water, sails and other nautical elements. The prints’ iridescence can be seen as either natural or industrial, a memory of the polluted landscape where the Wrbicans grew up in western Pennsylvania. While “Oil Tanker” is overwhelmingly dark, Sue Wrbican’s work shimmers with ambiguous beauty.

Dean Kessmann: Light Years, Chemical Days, and Digital Seconds; Chris Combs: Lossiness; and Sue Wrbican: This Iridescent Era Kessmann through Oct. 24, others through Oct. 17 at VisArts, 155 Gibbs St., Rockville.

Cosbert and Assefa

Both Ryan Cosbert and Redeat Assefa, paired in Mehari Sequar Gallery’s “AEffect,” are color field painters, but with very different approaches to depth. Assefa, an Ethiopia native who lives in Baltimore, makes seemingly translucent pictures with subtle gradations of a single color. Cosbert, a New Yorker, thickly layers her paintings — and not just with pigment.

Most of Cosbert’s pictures are checkerboard arrangements of tilelike squares, rendered loosely in multiple hues of sand-infused paint. While the repeated forms provide cohesion, the colors often intentionally clash. A closer look at a few pieces reveals a narrative level: A green-dominated picture collages pages from “The Negro Motorist Green Book,” a guide to traveling in the segregated mid-20th-century United States, and a white-and-blue one incorporates photos of Matthew Henson, the first Black explorer of the Arctic. The depths of Cosbert’s paintings are historical as well as actual.

Assefa’s pictures are as thin as Cosbert’s are chunky. Their luminous surfaces resemble the work of Mark Rothko and Leon Berkowitz, although with even less color contrast. The effect is, as the artist says in the show’s catalogue, to conjure “something that is both present and absent.” Her paintings can be seen as nearly empty or full to infinity.

Ryan Cosbert and Redeat Assefa: AEffect Though Oct. 17 at Mehari Sequar Gallery, 1402 H St. NE.

Fred Zafran

Traveling through the Metro rail system, Virginia photographer Fred Zafran thought of Greek mythology. “I imagine the River Styx and ferryman Charon transporting souls of travelers,” he writes of “The Transit of Shadows: An Allegory,” his Multiple Exposures Gallery show. But viewers might envision another place, just a bit less removed from life today: the 17th-century Netherlands of Vermeer and especially Rembrandt. The contrast of deep blacks and amber light in Zafran’s pictures has an Old Master quality that makes Metro stations appear more heavenly than infernal.

That’s not the only appeal of these photos, which are impeccably composed and intriguingly ephemeral. Relatively long exposures turn commuters into ghostly apparitions, and shooting through glass produces disorientingly layered imagery. (None of the pictures are double exposures or digitally altered.) The limited palette of the underground chambers accentuates the occasional contrasting color, whether the yellow of a woman’s coat or the blue of the seats in the latest generation of Metro cars. Interestingly, only one picture depicts the new cars, whose chilly color scheme breaks with Metro’s warm original one. In that sense, Zafran’s photos document the end of a literally golden age.

Fred Zafran: The Transit of Shadows: An Allegory Through Oct. 17 at Multiple Exposures Gallery, Torpedo Factory, 105 N. Union St., Alexandria.