# Writing Optic prompts

> How Optic understands your words, a structure that works every time, your own pictures, pointing at a Focus, and a template to copy.

Your words are the most important thing you give Optic. This page shows how Optic reads them and how to write a prompt that gets the film you imagine on the first try.

## How Optic understands your words

Optic reads your words **together with your clip, your pictures and your focuses** — not on their own. It looks at the stretch you chose, finds each thing you talk about, and works out every change you asked for: *which* subject, *what* it becomes, and *when*.

Three things follow from that:

1. **Only what you name changes.** Everything you do not mention comes from your original video — the room, the light, the camera, every movement and event, the timing, the sound. The performance too: a new subject's eyes, lips and every expression follow the original, whether or not anyone speaks; and whatever happens to the old subject — a mark, damage, a glow — happens to the new one at the same moments. You do not need to list what stays; you need to be exact about what changes.
2. **It reads the whole request at once.** You can ask for several changes in one prompt. Write each as its own sentence; Optic makes them all in the same film.
3. **One press makes it.** **Revise** is the payment, and everything after it — reading your clip, making your film — happens in that one run. There is no second press, so read your prompt once before you press it: [the checklist below](#before-you-press-revise) takes a minute. If the film cannot be made, your credits come back in full and the page says why.

Write in any language you like.

## A structure that works

Build each change from up to five parts. Most changes need only the first three.

| Part | Ask yourself | Example |
| --- | --- | --- |
| **What changes** | Which subject, or which part of it? | *her jacket* |
| **Into what** | What do I want to see instead — colour, material, shape, style? | *a long black wool coat* |
| **Which one** | Could it be confused with another subject? | *the woman on the left* or `#Focus 1` |
| **When** | The whole stretch, or only some seconds? | *from 0:12 to the end* |
| **What must stay** | Is something close to the change at risk? | *keep her scarf as it is* |

Put together: *"Change the jacket of the woman on the left into a long black wool coat. Keep her scarf as it is."*

## Be concrete

Optic makes what you describe, so describe what you would **see**. "Make it cooler", "better" or "more cinematic" leave the choice to chance. "Warm low sunlight from the left, long soft shadows, a slightly orange sky" does not.

- Name colours, materials, shapes and sizes.
- Say how something new fits: *"held in her right hand"*, *"on the front of the cup"*, *"in the same font and size"*.
- Keep one subject per sentence when you change several things.

## Using your own pictures

Add pictures with **Add** to show exactly what something should become — a person, a garment, a product, a logo. Each picture is named in order: **Image 1**, **Image 2** and so on.

- Type `@` in the words box and choose a picture: it writes `@Image 1`.
- **Your picture is what you want.** Everything a picture shows of the subject comes into your film — the face, the hair, what it wears, what it holds, even a tail. Choose the picture that shows the subject exactly as you want it seen.
- **Do not want something it shows?** Give a picture without it, or say so: *"Replace the man in the blue shirt with the person in @Image 1, without the cap."*
- **What the picture does not show stays as your video has it.** A close picture of a face brings the face; the clothes it does not show stay as they are in your video.
- Only the subject comes in — never the picture's background, its light or the pose it was taken in.
- For a character, use clear pictures where the face or the object is large and well lit.
- If you remove a picture, its mentions go with it; if you reorder pictures, the mentions follow.

## Pointing at a Focus

When your words could mean more than one subject — two men, three cars, a crowd — mark the one you mean with [Focus](https://routix.studio/help/focus/what-is-focus), then point at it:

- Type `#` in the words box. **Your focuses** lists each focus by the name you gave it — with its number, its colour and its moment — and typing a few letters finds it by name. Choose one, and it goes into your words as one piece. Written out, it is `#Focus 1`.
- *"Change the shirt of #Focus 1 to a navy linen shirt. The other man stays as he is."*

Your words hold a focus by its number, and a focus keeps its number even if you rename it, so your mentions never break. Focuses also tell Optic what you mean when you do not mention them, but naming them with `#` is the surest way. See [Focus in your prompt](https://routix.studio/help/focus/focus-in-your-prompt).

## Changing only some seconds

If a change should happen only for part of the stretch, say when, in the clip's own times as the timeline shows them: *"From 0:12 to the end, her hair is soaking wet."* The timeline's own times leave no doubt about which seconds you mean.

## How long a prompt can be

Up to 40,000 characters — far more than you need. Most strong prompts are two to five sentences. Longer is not better: every extra sentence is one more thing that might change.

## A template to copy

```text
Change [what changes — a subject, something it wears or holds, the text on screen, or the look]
into [what it becomes — colour, material, shape, style].
It is [which one — "the woman on the left", or #Focus 1].
[When — "for the whole stretch", or "from 0:12 to the end".]
[If you added pictures: … the [subject] in @Image 1 — and anything in it you do not want seen.]
[Only if something nearby is at risk: keep [what] as it is.]
```

Filled in: *"Change the jacket of #Focus 1 into the jacket in @Image 1. Keep her scarf and her bag as they are."*

## Before you press Revise

- Does each sentence name one change — what changes, and into what?
- Could "the man" or "the car" mean more than one? Mark it with Focus and mention it, or say which one.
- Does every `@` and `#` mention point at the picture or focus you mean — and does each picture show the subject exactly as you want it seen?
- Are the times where you expect them, and is anything close to a change that should stay said to stay?

If all four are right, press **Revise**. More examples: [Prompt examples](https://routix.studio/help/prompts/prompt-examples). Mistakes to avoid: [Common prompt mistakes](https://routix.studio/help/prompts/common-mistakes).

## Frequently asked questions

### Do I need to describe the whole scene?

No. Optic already sees your clip. Describe only what changes, and anything nearby that must not.

### Do I need to describe how the new person talks or moves?

No. The performance is your video's: the new subject's eyes, lips and every expression follow the original at the same moments, whether or not anyone speaks — and it moves as the old one moved.

### Can I ask for two or three changes at once?

Yes. Write each change as its own sentence; Optic makes them all in the same film.

### Why does my prompt change the action instead of the look?

If your words change what happens in the shot — people start doing something else — Optic does not revise it, because a revision keeps the story, and your credits come back. To change the story, use the chat: pick the moments, say what happens now, and ROUTIX makes them anew — see [Making video in the chat](https://routix.studio/help/chat/making-video-in-the-chat). Or make something new on a video model page.

Source: https://routix.studio/help/prompts/writing-optic-prompts · Updated 2026-10-24