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Black Forest LabsPrompt guide

FLUX.2 [klein] 4B Prompt Guide

How to write FLUX.2 [klein] 4B prompts: a structure that works, 4 example prompts for text to image and image edit, the settings that change the result and how to reference your own media. Copy any prompt into the Studio to try it.

Example prompts
4
2 tasks
Size
2K
1K · 2K
Aspect ratios
7
1:1 · 4:3 · 3:4 · 16:9
Per try from
$0.0007/image
1K
Try in Studio Call the API

Structure

A FLUX.2 [klein] 4B prompt, piece by piece

Write in this order and keep each part concrete. Physical detail works better than mood words.

  1. 01

    Subject

    The main subject and its key details: material, colour, expression, product features.

  2. 02

    Composition

    Framing and angle: close-up, flat lay, three-quarter view, rule of thirds, negative space.

  3. 03

    Setting and light

    Background, environment and lighting: studio softbox, golden hour, neon.

  4. 04

    Style

    Photo, illustration, 3D render or painting — plus lens or medium details.

  5. 05

    Edit instruction

    For edits, say what to change and what must stay the same: “replace the background, keep the product and its shadow”.

Examples

FLUX.2 [klein] 4B prompt examples

Prompts written for this model, grouped by task. Open one in the Studio, then change one part at a time.

  • Text to Image1:1
    Flat-lay of breakfast on a marble table, top-down, bright daylight
    Try in Studio
  • Image Edit3:4
    Make the jacket in image 1 bright yellow, keep everything else
    Try in Studio
  • Text to Image
    A cozy coffee shop interior with vintage furniture, morning light, photo
    Try in Studio
  • Image Edit
    Turn the room in image 1 into a snowy winter cabin; keep the furniture layout
    Try in Studio

By task

Prompting each FLUX.2 [klein] 4B task

Text to Image

Lead with the subject, then composition, setting, light and style. Quote any text that must appear in the image.

Image Edit

Describe the change, not the whole image. Name what must stay untouched so the model keeps it.

Referencing your own media

FLUX.2 [klein] 4B reference inputs and how to mention them
InputIn the promptLimits and rules
Input images
Image Edit · up to 4
see descriptionUp to 4 reference images to edit or combine. Refer to them as "image 1", "image 2"… in the prompt.

Settings

Settings that change the result

Set these next to the prompt — in the Studio or as API parameters.

FLUX.2 [klein] 4B generation settings
SettingOptionsEffect
Aspect ratio
aspect_ratio
1:1 · 4:3 · 3:4 · 16:9 · 9:16 · 3:2 · 2:3
default 1:1
Output image shape.
Price: 1:1 $0.0007/image
Resolution
resolution
1K · 2K
default 1K
1K ≈ 1 MP; 2K ≈ 4 MP (long side up to 2048 px).
Price: 1K $0.0007/image · 2K $0.0027/image
Seed
seed
—Use the same seed and settings to reproduce a result. Leave empty for random.

FAQ

FLUX.2 [klein] 4B prompting questions

There is no separate negative prompt for FLUX.2 [klein] 4B. Say what you want instead of what you don't, and keep unwanted elements out of the description.

Image Edit: Up to 4 reference images to edit or combine. Refer to them as "image 1", "image 2"… in the prompt.

Yes — set "seed" to a fixed number and keep the prompt and settings identical. Use the same seed and settings to reproduce a result. Leave empty for random.

Open FLUX.2 [klein] 4B in the Studio and paste any prompt from this page. Each run shows its exact price before you generate, and failed generations are refunded.