The tradition of the hand-altered photograph is nearly as old as the medium of photography itself. Taking various methods of hand-tinting into account, the photographic print has long served as a “canvas,” a ready-made support for pictorial intervention via paint, inks, collage, and much else. Derek Boshier and Berend Strik, very different artists, have both found fertile ground in this hybrid of techniques.

Mr. Boshier is a first-generation Pop artist, having studied alongside David Hockney and Allen Jones at the Royal College of Art in the early 1960s. He moved to America about 25 years ago and now resides in Los Angeles, where he teaches at UCLA. He is known for detail-laden drawings and hyperchromatic canvases that leaven social and political commentary with abundant humor.

Some three dozen examples of Mr. Boshier’s ongoing series of photo-based drawings in mixed media (mostly black ink) comprise “Extreme Makeover” at the gallery Flowers. None is larger than 14 by 11 inches, and each is vigorously improvisational. Mr. Boshier culls imagery from a variety of sources, including glossy magazine ads touting high-end consumer goods. His cheeky critique of fashion, consumerism, politics, and other culturally received values is a close cousin to the vandalized advertising billboard.

The best are the least labored, including a few in which the artist exposes and expands upon cues buried in the image. In “Macho Men,” the luxurious styling of the cockpit of a high-performance automobile becomes a wonderland of erect penises. A bit more subtle is “The Sensualists,” in which the S-curves of the biceps and thighs of a couple of buff male models are transformed into langorous serpents, hissing in the hot sun.

Many of these works are overlaid with quotes from commentators from the previous two centuries, notably Oscar Wilde: “Fashion is a form of ugliness so intolerable that we have to alter it every six months.” Regrettably, the artist is less assiduous in attributing his source photos. This oversight is forgivable when the image is familiar, such as the 1867 photograph by Julia Margaret Cameron known as “Call and I follow,” in which a young woman’s angular, droopy-eyed profile is nestled in a proto-pictorialist swirl of hair and drapery. In Mr. Boshier’s “Dreaming Sensuality,” based on a large detail of that image, the girl’s face is overlaid with a bristling, mazelike pattern of marks from which emerges a second profile, that of a man whispering in her ear.

A bland head shot of 1960s heartthrob Richard Hamilton is festooned with overlapping latticework reminiscent of the late, baroque mindscapes of Al Held, and titled “Researcher at the Alien Research Institute.” But “The Trouble with the Profit System” incorporates masterful photos of uninhabited corporate boardrooms featuring sprawling conference tables. Over them, Mr. Boshier sprinkles menacing silhouettes of military aircraft, which seem to flap around like bats. E.B. White is credited for the title (“the trouble with the profit system has always been that it was highly unprofitable to most people”), but the viewer is not informed that the striking photos are the entirely autonomous work of Jacqueline Hassink, from her mid-1990s series, “The Table of Power.”

In contrast to Mr. Boshier’s appropriationist approach, Mr. Strik’s recent work is predicated on his own photographs, taken on his travels through Africa. Highlighting his current show at the Jack Tilton Gallery, they depict dusty, rolling landscapes, vernacular architecture, and local people seen assembled as if in ceremony, or at ease. Onto these large black-and-white prints, which are sometimes affixed to canvas but more often stretched like one, the artist stitches meticulously shaped bits of fabric such as felt and tulle. Sometimes reinforcing the composition’s design and sometimes providing a fanciful counterpoint, these slithering swatches add a tactile jolt to the photo’s satin sheen, and delicate chroma to its silvery grays.

In “DJ,” ghostly, bluish clouds swirl above and around a man operating a polishing machine. These ephemeral, amorphous shapes might signify his lost, laboring hours, drifting out the window like smoke — or maybe just his idle thoughts. Does Mr. Strik intend to marry the dignity of domestic handicraft to the impersonal, mechanical photographic emulsion? To aestheticize quotidian African life behind a veil of European industrial production? To bring a vision of the veld to the Upper East Side? While the artist’s intentions are tantalizingly unclear, the results are visually stunning.

Mr. Strik is well aware of the history of the altered photograph. “De-unicefed” presents a gaggle of kids skeptically regarding the camera, some shirtless, others sporting jazzy prints. Discs of smoky scrim partially obscure their faces, a clear reference to John Baldessari’s strategy of concealing primary information in order to divert attention to the image’s secondary features. Here that incidental detail includes an empty plate extended toward the viewer.

In his earlier work, Mr. Strik covered much of the surface with dense embroidery in jarring colors, sometimes using pages from porn magazines. The new work, understated and haunting, is more introspective and substantial. Also included in the Tilton show are several smallish three-dimensional works that might be architectural models. They remind the viewer that the artist has worked on an environmental scale, as well as in performance and film. One hopes that Mr. Strik’s efforts do not become diffused but remain focused where they would seem to belong, in the pictorial realm.

Boshier until June 14 (1000 Madison Ave., between 77th and 78th streets, 212-439-1700).

Strik until June 28 (8 E. 76th St., between Madison and Fifth avenues, 212-737-2221).