Apply a Split-Field Diopter effect, making the nearest existing detail and a distant background feature simultaneously tack sharp on opposite sides of the frame. Leave an intermediate soft-focus zone and a subtle blurred vertical transition, with natural cinematic lighting and fine film grain. Keep the original subject and composition.
ASC describes the split diopter as ahalved optical attachment. One part of the image uses the close-up lens, the other only the main camera lens. This allows aclose face and adistant object to be kept in focus simultaneously. The dividing line is often hidden along adoor frame or other structure. This distinctive arrangement was particularly common between the 1970s and 1990s.
Distinction
This does not automatically mean continuous depth of field. Two separate zones of focus may be separated by ablurry or distorted seam; the close-up lens does not simply increase the depth of field everywhere.
Aftermath
Simultaneous sharpness can result from multiple optical zones.
Further examples · 7 images
02A Split-Field Composition Study in Old Westbury GardensA stone statue head in the foreground and a stone urn in the background are both in sharp focus. The split diopter creates a vertical blur between the two distinct focal planes.SavidgeMichael · CC BY 4.0 · Wikimedia Commons03A Split-Field View of a Mushroom in WonderlandA large mushroom in the immediate foreground remains sharp alongside the distant forest floor and tree trunk. A horizontal transition line separates the close-up lens effect from the background.SavidgeMichael · CC BY 4.0 · Wikimedia Commons04A Split-Field Composition Study in the BatteryA large flower cluster on the right is in focus while the distant red brick building on the left is also sharp. The dividing line is visible in the foliage between the subjects.SavidgeMichael · CC BY 4.0 · Wikimedia Commons05A Split-Field Experiment in the Massapequa Preserve, Revisted for the CommonsFungi on a foreground log and the texture of a log further back are both sharply defined. The image illustrates the technique by bridging two deep focal points in a forest setting.SavidgeMichael · CC BY 4.0 · Wikimedia Commons06Alternate Memory of a Split-Focus Shot at the National September 11 Memorial & MuseumA red flower in the foreground and a distant building are simultaneously sharp. The characteristic blurred vertical transition line is visible between the two focus planes, indicating the use of a split-field diopter lens.SavidgeMichael · CC BY-SA 4.0 · Wikimedia Commons07Groove and needle in close embrace from beginning to endA vertical transition zone is visible between the two turntable needles. Both foreground and background needle assemblies remain sharp, an effect achieved by using a partial close-up attachment on one side of the frame.Franz van Duns · CC BY-SA 4.0 · Wikimedia Commons
Question
Why is this image not a normal deep-focus shot?
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It has two optically separate focus areas instead of acontinuous sharp depth zone.
