Facial fifths
Face width read as five vertical strips: the edge of the face to the outer corner of the eye, the eye itself, the gap between the eyes, the other eye, and the outer corner back out to the edge of the face.
Also searched as rule of fifths face, five equal parts of the face and eye width fifths.
How to read it
The fifths describe how the face is laid out horizontally. They are not a target. The outer two depend on where the edge of the face falls, and in a 2D photo that edge is the silhouette, not the zygion underneath it.
The middle fifth (intercanthal) exceeds the eye-length fifths in most East Asian and many other adults. Descriptive only.
Conformity in published samples: na white 41% · east asian 0%
Why every value has an error bar
Every value Canthion reports carries a 1σ uncertainty propagated from MediaPipe Face Mesh's published accuracy (3.96% of inter-ocular distance mean absolute error per landmark, Kartynnik 2019). On a typical photo with 300 px between the pupils, that is about 12 px of wander on every point. Small ratios and angles inherit it, so their intervals are wide. A number without an interval is a number pretending to be more precise than it is.
References
- Farkas, Hreczko, Kolar & Munro (1985). Vertical and horizontal proportions of the face in young adult North American Caucasians: revision of neoclassical canons. Plast Reconstr Surg 75(3):328–338. pubmed.ncbi.nlm.nih.gov/3883374/
- Jayaratne, Deutsch, McGrath & Zwahlen (2012). Are Neoclassical Canons Valid for Southern Chinese Faces? PLoS ONE 7(12):e52593. doi.org/10.1371/journal.pone.0052593
Common questions
What are facial fifths?
Face width read as five vertical strips: the edge of the face to the outer corner of the eye, the eye itself, the gap between the eyes, the other eye, and the outer corner back out to the edge of the face. The canon claims five equal fifths (20% each).
How are facial fifths measured from a photo?
They are computed from the face-mesh landmarks (zy_R, ex_R, en_R, en_L, ex_L, zy_L): [dist(zy_R,ex_R), dist(ex_R,en_R), dist(en_R,en_L), dist(en_L,ex_L), dist(ex_L,zy_L)] / dist(zy_R,zy_L). Every value carries a 1σ error bar propagated from the landmark detector's published accuracy, with a floor of ± 1, so a small difference inside the interval is not a difference.
How should facial fifths be read?
The fifths describe how the face is laid out horizontally. They are not a target. The outer two depend on where the edge of the face falls, and in a 2D photo that edge is the silhouette, not the zygion underneath it.
The five-equal-fifths rule is a neoclassical canon; that page has what share of each measured sample actually follows it.
Related measurements
The rest of the whole face set, then the nearest measurements elsewhere on the face. Every one is computed on the same photograph, in the same run, with its own error bar.
Also: how bone-level measurements are taken from a photo · methodology · glossary · all 35 insight pages