How to Prompt a Before-and-After Pair that Matches

Anyone selling a clean, a plate, or a makeup job can prompt a before-and-after image pair that matches in five moves: write one shared lock, name a single variable, shoot the hero first, force the same crop and lens, then reject extra drift. Do it in Midjourney, Flux, or Grok Imagine before two pretty frames refuse to sit on the same slide.

A pair is a controlled experiment. One thing changes. If the lamp, the lens, and the face also change, you have two ads, not a before and after.

Revision polishes one frame. A pair is two frames under one freeze. Read the three-pass image revision loop if you still remix forever, then lock the experiment.

Prompt a before-and-after pair that matches

Share a lock. Name one variable. Hero first. Match the camera. Reject drift.

1. Write one shared lock for both frames

The lock is everything that must be true in both pictures:

"One small bathroom, white subway tile, left-hand window, pedestal sink, brass tap, phone-high crop, no people, held still."

Or for a face: the full character freeze — age, hair, wardrobe, pose, crop — plus the room.

If subject and atmosphere are still mixed, split them into layers before you pair. The variable will leak into the lock if they share a sentence.

Paste the lock at the top of both prompts. Retyping is how the tap turns chrome in the after.

2. Name the single variable

One noun or one state. Write it as a toggle.

"Variable only: sink and mirror dirty, toothpaste spots, water spots, towel slung. Versus: sink and mirror clean, towel folded, dry porcelain."

Not: dirty plus new plants plus new paint. That is a renovation storyboard, a different skill.

Good variables: empty plate / plated dish, scuffed toe / restored leather, bare face / specified makeup, winter porch / the same porch with leaves.

The variable gets its own block. Segment it so it cannot rewrite the tile.

3. Generate the hero first

The hero is usually the after: the clean, the plated, the restored. Generate it until the lock holds. Freeze that image as canon. Note the seed or ID.

Then generate the before from that canon: same lock, same reference, variable flipped, no other edits.

If you generate a sloppy before first, the after will "improve" the room and you will lose the experiment.

4. Force matching crop, lens, and palette

Add the same technical line to both:

"Technical: 35mm look, straight-on, same crop marks, same white balance, no new practicals."

If the after goes wider "to show the clean floor," you broke the pair. A viewer should believe one tripod, two moments.

Do not let Midjourney beautify the after with a new grade. Do not let Flux add a window that "reads cleaner." Windows are not a cleaning variable unless you named glass as the variable.

5. Reject if anything besides the variable moved

Checklist, both frames:

• Tile, tap, crop, lens match.
• People match, or both have none.
• Palette matches except where the variable forces a local change (a stain that leaves).
• No new props in the after "as a reward."

A plant that appears in the clean bathroom is a lie. A slimmer jaw in the makeup after is a lie. Reject. Rerun. Do not inpaint the plant out and call the pair honest.

Save the shared lock and the toggle. Pull them from the Promptcrates library of image skills.

Reusable skill card

Trigger: You need two frames that claim a change and you are about to prompt them as two separate pretty pictures.

Input: One shared lock, one variable written as a toggle, a hero-first order, identical technical line, prior ID for the second frame.

Output: Two files. Only the variable differs. Same crop, lens, and lock tokens.

Stop: After both frames pass the checklist. No split-screen generate. No reward props. No beauty drift.

Takeaways

• One shared lock, pasted, not remembered.
• One variable. Two nouns are two stories.
• Hero first, usually the after. Then walk it backward.
• Same crop, lens, and white balance. One tripod.
• Reject extra drift. A prettier jaw is a recast.