What defines it
- A single main light placed off to one side and above the subject, so that one half of the face is lit and the other falls into shadow.
- A triangle of light on the shadowed cheek, formed where light passing the nose reaches the cheek below the eye. Its presence is what makes the setup Rembrandt rather than generic side lighting.
- The accepted answer counts it among the handful of basic portrait lighting patterns, so it is a named starting point rather than an unusual technique.
- One answer drew a further distinction, calling it Rembrandt when the triangle falls on the side of the face turned towards the camera and giving a different name to the reverse.
Where the name comes from
From the painter, whose portraits repeatedly use a single off-axis light source producing exactly this pattern. One answer supplied the art-historical side, pointing at paintings where the same shape appears and noting the direct resemblance to modern photographic examples. It is a case of photography naming something it found already solved.
What it is for
The effect the thread kept returning to is strong contrast used to describe shape — light and dark doing the work of showing that a face is three-dimensional. One answer described building on it with a second light on the background, placed close and at an angle so it falls off across the frame, which sets the shadowed side of the face in silhouette against a brighter field behind.
Using it
- Move the light until the triangle appears. Its position and size are controlled by the height and angle of the light relative to the nose.
- It suits subjects where a defined, sculpted look is wanted rather than an even one.
- Because half the face is in shadow, it emphasises structure — which is a stylistic decision about the person, not a neutral default.
- It needs only one light, which is why it remains a standard exercise for learning portrait lighting.