# FLUX 3 Image Klein prompting guide

> Updated 2026-10-16 · https://imageklein.com/flux-3-image-klein-prompting

FLUX 3 Image Klein follows long, specific prompts much better than short ones: its model card warns that short prompts give generic results, which is why BFL ships a prompt upsampler that rewrites them into full captions. Describe subject, setting, light, camera and style; for edits, say only what should change.

## 1. Write the whole picture

Subject → action → setting → light → camera → style. Compare:

```
Short:  a cat on a sofa
Better: A close-up photo of a ginger cat curled up asleep on a mustard-yellow
        velvet sofa, late-afternoon sun from a window on the left, shallow depth
        of field, 50mm lens, warm natural colors.
```

Too lazy to write long prompts? Use the prompt upsampler (`flux-3-image-klein-pup`, built into the reference CLI and the API's prompt upsampling).

## 2. Text in the image

FLUX 3 Image Klein can render text. Put the exact words in quotes and say where they go: *a vintage enamel sign that reads "OPEN 24 HOURS" above the door*. Check spelling in the result — the model card says rendered text can still come out wrong.

## 3. Editing one image

State the change and what stays: *Make it night with heavy snow; keep the tram, the street and the camera angle the same.* Through the API, pixel restoration keeps untouched areas pixel-identical.

## 4. Several reference images

You can pass up to 10 images. Refer to them by their position so the model knows which is which — for example *the woman from image 1 wearing the jacket from image 2, standing in the room from image 3*. With bounding boxes, the input is written as `<ref_image_0>`.

## 5. Control the layout

When position matters, end the prompt with bounding boxes — see the [bounding-box guide](https://imageklein.com/flux-3-image-klein-bounding-boxes).

## Don't

- Don't put real people in fake or intimate scenes, or copy someone's likeness without consent — the license forbids it.- Don't expect factual accuracy: the model draws, it doesn't look things up.

## FAQ

**Why are my FLUX 3 Image Klein results generic?**
Short prompts give generic images. Write a full description (subject, setting, light, camera, style) or turn on prompt upsampling.

**Can FLUX 3 Image Klein write text in images?**
Yes. Put the exact text in quotes; check the result, since rendered text can still be inaccurate.


## Sources

- [Hugging Face — black-forest-labs/flux-3-image-klein (model card)](https://huggingface.co/black-forest-labs/flux-3-image-klein)
- [Black Forest Labs — FLUX 3 Image Klein (blog, Oct 15, 2026)](https://bfl.ai/blog/flux-3-image-klein)
- [BFL docs — FLUX 3 Image bounding boxes](https://docs.bfl.ai/flux_3/flux3_image_bounding_boxes)
- [BFL docs — API release notes](https://docs.bfl.ml/release-notes)