How to stop a face, a product, or a logo from drifting
Commercial work does not need one pretty frame. It needs the same face in four outfits, the same bottle at three angles, the same mark still readable on a flag. A lock is a constraint, not a style.
The hard problem in commercial image models is not beauty. It is sameness. Models are trained to invent. If you do not name what is sacred, they will “improve” it: smooth the bone structure, redraw the logo as a cooler cousin, turn one bottle into four relatives.
Write the lock first
There are three common locks. Put the lock in the first sentence of the subject block. Do not tack it on at the end as a footnote.
- Identity: this face, this bone structure, this mole, this hairline. Usually from one uploaded still.
- Object: this bottle, this stitch, this exact frost on the glass, this label layout.
- Mark: this logo, these colors, this letterspacing. Do not redraw.
“Use the uploaded image as a strict identity source, zero deviation” is a different instruction from “inspired by the reference.” The second gives the model permission to cast a lookalike. Logos work the same way. Say how the mark is allowed to appear — printed on fabric, engraved in metal, hanging as a flag. Those are integration modes. “Make a cooler version of this logo” is how you get a different brand.
subject.reference: uploaded still is the strict identity source subject.consistency: zero deviation subject.do_not: beautify bone structure, move the mole, restyle the hairline integration: printed on fabric only preserve: original colors, shape, letterspacing do_not: redraw, recolor, substitute a similar mark
Freeze materials. Let pose move.
Consistency dies when you change too much at once. If the face is locked, keep the lighting recipe and the lens for the whole set; vary outfit or crop. If the bottle is locked, keep the softbox and the surface; vary angle — hero, three-quarter, macro of the pump.
A four-panel grid holds when identity, makeup, skin, and background are frozen and only the crop walks a little. It fails when each panel is rewritten as a fresh “cinematic portrait” that happens to share a name. A name is not a lock. The lock is the sentence that forbids deviation, plus the light you did not change.
Where the lock usually breaks
- Relighting from daylight to neon between frames while demanding the same face.
- Switching from 85mm to wide without restating that identity still holds.
- Asking for a smile, a new part, and a new jacket in one step.
- Making the model invent readable type on packaging — it will hallucinate a cousin of your label.
- Style words that fight the reference: strict identity photo plus anime.
If you must change the light, build a bridge: same identity, same clothes, new light only. Once that holds, change the clothes. Skipping the bridge looks like two actors.
A protocol that holds
- One reference. Not three. Three references are an average.
- State the lock in one sentence at the top.
- Copy the lighting and lens block into every frame of the set.
- Change a single production variable per generation.
- If the lock slips, do not add adjectives. Restate the lock and delete the competing instruction.
This is slower than rolling the dice. It is also the only way the output belongs in a lookbook, a product page, or a brand kit. Pretty is an accident. Sameness is a constraint you wrote down.