Where the light comes from
What shadow does each light-position tag put on a face?
Light direction is the single biggest variable in a portrait. The same face reads completely differently depending on where the light sits.
This one failed once too. The base said plain interior wall, and the model kept inventing a window — deciding where the light came from before the tag could. On a dark studio background the window went away, but even then the light on the face did not separate much across the four cuts below.
Every cut below shares one seed, one base prompt and one sampler setting, and differs only by the tag marked in amber.
What each cut shows
sidelighting- Side light was asked for, but the face is evenly lit on both sides with no half-face shadow; the side light shows only as one side of the blouse being a little brighter.
backlighting- Light from behind. The hair and shoulder line catch a bright edge while the face darkens. What people call rim light actually comes from this tag.
uplighting- Light from below does not show: the throat under the jaw is shaded as in the other cuts, so the light still reads as coming from above.
butterfly lighting- Instead of the lighting setup, a literal butterfly appeared. No butterfly-shaped shadow shows under the nose, and she turns in profile toward the butterfly.
How these were made
Shared prompt
masterpiece, best quality, amazing quality, very awa, 1girl, solo, mature female, adult woman, short black hair, brown eyes, white blouse, upper body, dark studio, black background, <tag slot>
Tap a tag to carry it over to the builder
Negative prompt
school uniform, pleated skirt, blazer, serafuku, child, loli, teenage, bad quality, worst quality, worst detail, sketch, censor, jpeg artifacts, watermark, signature, text, extra limbs, bad hands, bad anatomy
Model
rinFlanimeIllustrious_v30 · euler_ancestral/normal · steps 28 · CFG 5 · 896×1152 · seed 777002
Takeaway
Even with a dark background leaving the light undecided, none of the four reshaped the light on the face much. The visible change is the glow around the hair in backlighting, and butterfly_lighting drew a butterfly. Direction tags alone did not set the shadows on the face here.
How far this result reaches
uplighting and butterfly_lighting did not come through as lighting on this checkpoint: uplighting shows no light from below, and butterfly_lighting summoned an actual butterfly.
Measured on a single Stable Diffusion family checkpoint. The same tags can behave differently on NovelAI, Midjourney or another checkpoint. This is a reference point, not a verdict.