# A→B Motion Brief: Action, Lens, Pacing Checklist

![A → B contract — Action, Lens, Pacing serve the poles only](https://cdn.hashnode.com/uploads/gql/6ac7155f8cadc38d9e483af7/ee3f8128-e2d9-4a61-a8d2-0c038e46da66.png)

*MixVio illustrative card: **Action · Lens · Pacing** — middle motion serves A→B only — our_generated structure graphic.*

Builders who already own a start still and an end still still lose takes when the **motion brief** describes a new scene instead of the bridge. This checklist forces middle motion to serve **first → last** only — Action, Lens, and Pacing as a contract, not a mood board.

Specs match MixVio’s Image-to-Video tool and model pages (checked 2026-11-03). **Confirm the live credit quote before every Generate.** Soft promo; no price stacks.

## Preconditions (poles locked)

Before you write a single motion line:

1. You have rights to **both** JPEG/PNG/WebP poles.
2. Silhouette, face/product angle, materials/logo, light, and background anchors agree across poles — or the conflict is intentional and documented.
3. You picked an **end-frame-capable** MixVio catalog route for this take (not a start-only Fast path; not a route whose FAQ denies last-frame photos).

Optional helpers for a missing pole: MixVio **AI Image Generator** or **Image to Image**. They are **not** a required single-model pipeline into any I2V route.

On [MixVio home](https://mixvio.ai/?utm_source=hashnode&utm_medium=article&utm_campaign=first-last-frame-control-remix&utm_content=first-last-frame-control-remix-hashnode-intro) the contract sits in a multi-model Image-to-Video workspace — keep one owned pair; change only the brief.

## The A→B checklist

Use this as a paste-ready brief. Fill every line; delete adjectives that do not move you toward the last frame.

| Field | Rule | Pass example | Fail example |
|---|---|---|---|
| **Action** | One transition that **lands** on the last frame | “Stand → seated; arm lowers once” | “Make them move cinematically” |
| **Lens** | Motivated by the **end** composition | “Hold; tiny push-in into end framing” | “Orbit and whip pan” |
| **Pacing** | Ease A→B; short test first | “Ease into last pose; 5s test” | “Max energy the whole take” |
| **Preserve (implicit)** | Identity already locked in poles — do not rewrite | “Keep jacket color + face angle” | “Change outfit mid-take” |

**Weak briefs** re-describe both stills or invent a third scene. **Strong briefs** name only the bridge.

Three stronger lines you can adapt:

- “Only the raised arm completes the last-frame silhouette; hold lens; no whip pans; 5s.”
- “Product rotates to the end still’s angle; soft light unchanged; short take.”
- “Sit-down lands on last pose; locked camera; ease; discard if walk-off appears.”

## Run order on the desk

1. Attach start + (when the route allows) last frame.
2. Paste Action / Lens / Pacing — nothing else.
3. Prefer **short + lower-res** until the bridge is honest.
4. Change **one** middle variable per take.
5. Reject any take that invents an exit the last frame does not own.

Open the [A-to-B motion-brief desk](https://mixvio.ai/tools/image-to-video?utm_source=hashnode&utm_medium=article&utm_campaign=first-last-frame-control-remix&utm_content=first-last-frame-control-remix-hashnode-inline#effect-workspace) in **Chrome**. Prefill spends nothing until Generate.

## Route note (end-frame capable vs not)

End-frame-capable examples in this facts set include Seedance 2.5 / 2.0, Kling 4.0, MiniMax H3, Veo 3.1, Wan 3.0, PixVerse V6, and Gemini Omni Flash 1.1 where the model page says so. **Veo 3.1 Fast** is start-only I2V here; **Vidu Q4** FAQ states no last-frame photo — do not put an end pole on those routes and expect it to bind.

Vendor background: [Kling 4.0 user guide](https://kling.ai/quickstart/kling-4-model-user-guide) and [Seedance 2.5 page](https://seed.bytedance.com/en/seedance2_5). MixVio limits and the live reservation win.

## Live quote anchors (re-check every take)

Credits follow **model + duration + resolution**. Model-page anchors only:

- Seedance 2.0 — Mini 4s·480p=**5**; Standard from **19**; Std 5s·720p=**49**; Std 5s·1080p=**118**
- Seedance 2.5 — 4s·480p=**27** (page example)
- Kling 4.0 — default 5s·720p=**43**
- MiniMax H3 — default 5s·768p=**8**; Veo 3.1 720p=**68**; Gemini Omni Flash from **15**

![MixVio workspace live credit quote example](https://cdn.hashnode.com/uploads/gql/6ac7155f8cadc38d9e483af7/d5f08594-1d70-41c2-879c-fbd7cb212432.png)

*MixVio workspace capture: live Generate quote area (signed-in UI still; digits in-frame are a past quote example and may differ from current model-page anchors) — confirm your own reservation before Generate.*

Failed or safety-cancelled runs **release the reservation** on MixVio’s pricing page; Kling’s “failed runs return reserved credits” is compatible. Free-plan video is **evaluation only**; paid-plan outputs may be commercial under MixVio ToS **and** each provider’s rules when you have rights to both poles and the prompt.


## Paste template (copy into the prompt box)

```
Action: <one transition that lands on the last frame>
Lens: <hold | slow push-in motivated by end framing>
Pacing: <ease A→B; duration for this test>
Preserve: <identity already in poles — jacket / face angle / logo>
```

Keep the template boring on purpose. Boring briefs that land beat cinematic briefs that invent a third scene.

## Iteration after the first pass

If the bridge almost works: change one field only. If identity melts: stop iterating motion — re-check pole alignment (silhouette, materials, light) before you spend again. If the route ignores your last frame: confirm you did not pick a start-only path in this facts set.

## Checklist FAQ

**Can I skip Lens and only write Action?**

You can, but the model will invent camera. If the last frame’s framing matters, write Lens.

**Is this a multi-cell storyboard checklist?**

No — this is a **two-pole** A→B brief. Multi-grid boards help when beats change across many cells; here two owned stills plus three fields are enough.

## Bottom line

If middle motion does not serve first→last, the brief failed — not the model. Fill Action / Lens / Pacing, stay on end-frame-capable routes, iterate one variable at a time, and **read the live quote**. [Run the A→B checklist on MixVio](https://mixvio.ai/tools/image-to-video?utm_source=hashnode&utm_medium=article&utm_campaign=first-last-frame-control-remix&utm_content=first-last-frame-control-remix-hashnode-cta#effect-workspace).