Four Looks, One Rig

Portrait lighting has a small vocabulary of standard setups, worked out over decades and named after the painters, studios and effects they produce. They are worth offering as presets because they are genuinely good starting points, and worth understanding because a preset that lands in the wrong place on a particular face is a preset that has to be nudged, and nudging is easier when you know what the setup was trying to do.

The four

Rembrandt puts the key high and around forty-five degrees to one side. The shadow of the nose reaches down toward the shadow of the cheek and stops just short, leaving a small triangle of light on the shadowed side of the face. That triangle is the whole point: it is the signature, it is what the setup is named for, and when it closes up or runs away into the shadow the look is gone. It is sculptural and serious, and it suits most faces.

Butterfly, also called Paramount after the studio that used it constantly, puts the key high and directly in front. The shadow under the nose is small, centered and shaped roughly like a butterfly. It is symmetrical, flattering, emphasises cheekbones, and is the glamour-portrait light. It is less kind to deep-set eyes, where the height that produces the effect also produces shadow where you want none.

Split puts the key at ninety degrees to the side. Half the face is lit, half is in shadow, and the line between them runs down the middle. It is the most dramatic of the four, it does not flatter, and that is frequently the reason to choose it.

Softbox is less a position than a quality: a large source, close in, slightly to one side and slightly above. The shadows are open and their edges are wide, texture is played down, and the result is clean and modern. It is the safest of the four and the one that asks the least of the depth behind the photo.

The hard part is knowing where the subject is

Every one of those descriptions is relative to a face. Forty-five degrees from what, high relative to what, close by how much — all of it is meaningless without knowing where the subject is and how large. A preset expressed in absolute coordinates would work on the photograph it was designed for and fail on the next one.

Depth is what makes this solvable. The subject of a portrait is the nearest coherent mass in the frame, and a depth map states plainly which region that is and roughly how far it extends in each direction. From that you get a center and a size, and a look can be expressed in units of the subject rather than units of the image: this far to the side in terms of the subject's own width, this far in front in terms of its own depth. The same description then produces the same lighting on a tight headshot and on a half-length portrait taken across a room.

It also sets the sizes. A softbox is only soft in relation to the thing it is lighting; a source the size of a head, a handspan away, is soft, and the same source across a hall is a point. Size has to scale with the subject too, or the look survives the change of framing in name only.

Defaults are part of the look

Position is not the whole recipe. A Rembrandt key that is large and soft stops producing the triangle, because the shadow edges that form it have spread out and met. A split light with a strong fill is no longer split. The power ratio between key and fill, the size of each source, and the warmth all belong to the preset as much as the angles do, and getting them wrong produces a setup that is in the right place and looks like nothing in particular.

Why it stops being a preset

A look is a first guess made without seeing the photograph. It does not know the head is turned, or that the subject is off to one side, or that there is a bright window behind them. It will be close, and it will rarely be finished.

Which is the intended outcome. The value of the four looks is not that one of them is right, but that each puts three lights into a sensible arrangement in one tap, so the work starts from a real rig rather than from a blank scene and three lights at the origin. The moment a light is moved it is no longer Rembrandt, or Butterfly, and nothing is lost by that. It was never the destination.