Nothing says anthropocentric like a good old-fashioned portrait. Isolated, regally upright, and centered among objects chosen to enhance its prestige, classical portraiture celebrates men and women as the measures of all things. In JuxtaPOSE, the group exhibit currently on view at The Arts Fund, curator Ashley Woods Hollister has gathered works by four artists — Connie Connally, Sommer Roman, Lindsey Ross, and Leslie Lewis Sigler — into a provocative examination of what portraiture might become in an expanded field extending beyond the limits of unaided human perception.

For millennia, human understanding has been confined to our species umwelt, meaning the world as it is experienced by a particular organism, in this case that of Homo sapiens. As we learn more about how other species perceive the world — and in particular how they depend for evolutionary survival on senses we lack, such as a bat’s sonar hearing or a migratory bird’s internal magnetic compass — our knowledge of the world is revealed to be what it has been all along: a small sliver of the fabric of physical reality as a whole.

In Sommer Roman’s striking series of Cell Portraits, the cellular structures of two distinct organisms, such as that of a human eyelid and a clover plant, are resized, translated, and reproduced as composite images through a painstaking process of manual drawing with pen and ink. In the giant, mandala-like “Cell Portrait 4 (I Feel You, You Feel Me),” Roman enmeshes her hyper-detailed drawings of human sense receptors with images of other organic matter into an emblem of the complex chemical interchanges that make perception happen. Roman exhausted more than 2,000 disposable pens in the course of making these images, but in the experience of viewing these works in person, undertones of hypergraphia quickly give way to meditative awe at the microscopic realities that are within us but exist beyond the scope of our naked eyes.

As a counterweight or “juxtaPOSE” to Roman’s drawings, Hollister has enlisted photographer Lindsey Ross, who is here represented by a spectacular series of ambrotypes called Nymphs in Narnia. Captured by her vintage large-format, wet-plate collodion camera, these landscapes feature nude female figures reminiscent of those found in neoclassical paintings. The complex, intricately balanced textures traced by light onto these giant plates yield yet another reality beyond that of unaided human perception. Like the microscope that allows Roman to see the cells, the wet-plate camera gives Ross access to a world that exists in reality but that suggests a spiritual dimension, a “Narnia,” in which nymphs are not only possible but likely. These extravagant images chart a territory that’s at once mysterious and matter-of-fact, mythological and representational, natural and supernatural.

In the pairing of Connally and Leslie Lewis Sigler, the show takes another approach to the puzzle of the portrait. This time the lines that get blurred are the ones that divide family members and generations from one another and inanimate objects from the living presences that bring them to life. Sigler collects silverware and paints still-life portraits that emphasize the degree to which use gives character to the forks, knives, spoons, and bowls over time. In addition to her highly realistic, carefully focused representations, there is also a suitcase on display filled with the most disconcerting dinner service I have ever encountered, something that has to be seen to be believed.

Connally offers both the show’s most ambitious traditional portrait in her large painting of “Zach at 13,” and the show’s most enigmatically personal work in her construct of a hand-carved wooden box containing two paintings titled “My Mother, My Self.” As an essay on the outer boundaries of our idea of the portrait, JuxtaPOSE makes a bold statement.

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JuxtaPOSE shows at The Arts Fund Gallery (205C Santa Barbara St.) through July 14. There will be a panel discussion featuring the four artists in the gallery on Friday, July 13, 6-7 p.m. See artsfundsb.org.