Has there ever been anything (technobabble or otherwise) expanding the fiction of Blade Runner's ESPER machines? Otherwise it just appears to be a magical future 3D photo exploring device.
The ESPER machine was able to shift the viewer's point of view to see around obstructions and do near infinite zooming in. In the real world, plenoptic light-field cameras can already do half of that; a microlens array in front of the sensor pixels allows seeing around foreground obstructions to a limited extent. But this virtual camera move is always at the cost of image resolution, so you trade some image quality in exchange for this feature. This would limit the usefulness of zooming after doing a camera move. But if you started with an exceedingly high resolution light-field capture, you could achieve most of what the Blade Runner ESPER machine does.
I think the theory in ESPER machine in the movie is that any surface in a given room is actually receiving all the light bouncing around in that room, including, perhaps light coming from the window if it is open, just like a mirror, only that the reflected light is distorted to the eyes because of the irregularity of the surface topology and/or the surface's color. And just like a mirror in a room, you can practically see the entire room if you position yourself and the mirror at the proper angles. The computer in the movie is able to reconstruct the distorted light through some powerful algorithm, it seems.