> ## Documentation Index
> Fetch the complete documentation index at: https://docs.runchat.com/llms.txt
> Use this file to discover all available pages before exploring further.

# JSON prompting: control lighting

> Describe an image as editable JSON, change the lighting fields, and re-render

Long prose prompts are hard to tweak. This workflow describes an image as structured JSON with a field for each thing you might change, shows the fields as dropdowns in an app, and re-renders from your edits.

![A house photograph in late afternoon light and the same view re-rendered at blue hour](https://mintcdn.com/runchat/ExzxwftWKPCOoCF3/images/examples/json-lighting.webp?fit=max\&auto=format\&n=ExzxwftWKPCOoCF3\&q=85\&s=782b37b14dd56f691a812d5975e9d0d1)

> [card] [Open the example workflow](https://runchat.com/editor?id=efdd766a-c4a1-4665-b41f-710777a2bc29)
>
> Make a copy of this workflow in your account to try it with your own images.

## How it works

1. **Describe as JSON** is an [Agent](https://docs.runchat.com/node-reference/nodes/agent.md) with a vision model and a JSON output format. It lists 14 to 20 fields across Environment, Lighting, Materials, Objects, Camera and Photography, each with its current value and five alternatives.
2. **Scene editor** is an app that shows every field as a dropdown. Changed fields are highlighted and listed, and you can add free-text notes.
3. **Render (Flux 3)** re-renders the image from the edited JSON and applies only what changed. This example sets time of day to *blue hour*, light quality to *cool diffuse skylight* and sky to *uniform deep blue*, with interior lights on.

![The Scene editor app showing the image, the changed lighting fields, and dropdowns for every field](https://mintcdn.com/runchat/ExzxwftWKPCOoCF3/images/examples/json-scene-editor.webp?fit=max\&auto=format\&n=ExzxwftWKPCOoCF3\&q=85\&s=e11a5d29c028eef06cf16998febf25e1)

## Tips

* Run **Describe as JSON** again after swapping in your own image.
* The same app drives [materials](https://docs.runchat.com/examples/json-materials.md), [objects](https://docs.runchat.com/examples/json-objects.md) and [photographic style](https://docs.runchat.com/examples/json-photographic-style.md).


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