PolarPro has introduced the Split 50, a circular lens filter that covers only half of its surface with optical glass while leaving the other half unmodified. The asymmetry is the product’s essential feature. The Split 50 is a split diopter — a category of filter with a history in professional cinematography — adapted into a compact, threaded format for use in both photography and filmmaking.

The optical mechanism is straightforward: one half of the filter incorporates a +2 diopter element, which functions similarly to a close-up filter: it effectively shortens the focal distance for the portion of the frame it covers. The other half leaves the image unaltered. When both halves are in use simultaneously, two subjects at substantially different distances from the lens can appear in focus within the same frame, a result that would otherwise require stopping down to a very small aperture — at the cost of losing the shallow depth-of-field characteristics typical of wide aperture shooting. The Split 50 allows this dual-focus effect to coexist with the background separation of an open aperture, though PolarPro notes the effect functions most cleanly between f/1.2 and f/4.

The technique has appeared in cinema for decades. Among the films most associated with the split diopter are Citizen Kane, All the President’s Men, Reservoir Dogs, and The Untouchables, where cinematographers used it to build visual tension by holding two spatially separated subjects — often a foreground and background figure — in simultaneous focus. The effect draws the eye to the relationship between the two planes rather than directing it toward a single point, which is part of its appeal in narrative filmmaking.

The Split 50 rotates a full 360 degrees, allowing the dividing line between the diopter half and the clear half to be positioned anywhere across the frame. The choice of where that line falls is part of the compositional decision: aligning it through empty areas of the frame can make the transition less visible, while placing it deliberately through a subject can exaggerate the split as a stylistic effect.