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FLUX.2 [klein] works best when you describe scenes like a novelist, not a search engine. Write flowing prose with lighting details, and the model delivers.
No prompt upsampling: [klein] does not auto-enhance your prompts. What you write is what you get—so be descriptive.

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Write Like a Novelist

Describe your scene as flowing prose—subject first, then setting, details, and lighting. This gives [klein] clear relationships between elements.
Portrait with soft, warm tone

'A woman with short, blonde hair is posing against a light, neutral background. She is wearing colorful earrings and a necklace, resting her chin on her hand. The image has a soft, warm tone with a minimalist style.'

Do this

“A woman with short, blonde hair is posing against a light, neutral background. She is wearing colorful earrings and a necklace, resting her chin on her hand.”

Not this

“woman, blonde, short hair, neutral background, earrings, colorful, necklace, hand on chin, portrait, soft lighting”

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Basic Prompt Structure

Use this framework for reliable results:
Subject → Setting → Details → Lighting → Atmosphere
ElementPurposeExample
SubjectWhat the image is about”A weathered fisherman in his late sixties”
SettingWhere the scene takes place”stands at the bow of a small wooden boat”
DetailsSpecific visual elements”wearing a salt-stained wool sweater, hands gripping frayed rope”
LightingHow light shapes the scene”golden hour sunlight filters through morning mist”
AtmosphereMood and emotional tone”creating a sense of quiet determination and solitude”

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Lighting: The Most Important Element

Lighting has the single greatest impact on [klein] output quality. Describe it like a photographer would.
Instead of “good lighting,” write “soft, diffused light from a large window camera-left, creating gentle shadows that define the subject’s features.”
Portrait with soft, warm tone

Soft diffused light

Architecture with dramatic light and shadow

Dramatic side lighting

Lioness with cubs in golden savanna light

Golden hour backlight

What to describe:
  • Source: natural, artificial, ambient
  • Quality: soft, harsh, diffused, direct
  • Direction: side, back, overhead, fill
  • Temperature: warm, cool, golden, blue
  • Interaction: catches, filters, reflects on surfaces
Example lighting phrases:
  • “soft, diffused natural light filtering through sheer curtains”
  • “dramatic side lighting creating deep shadows and highlights”
  • “golden hour backlighting with lens flare”
  • “overcast light creating even, shadow-free illumination”

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Word Order Matters

[klein] pays more attention to what comes first. Front-load your most important elements. Priority: Main subject → Key action → Style → Context → Secondary details
Strong word order:“An elderly woman with silver hair carefully arranges wildflowers in a ceramic vase. Soft afternoon light streams through lace curtains, casting delicate shadows across her focused expression.”Subject and action lead.
Weak word order:“In a warm, nostalgic room with antique furniture, soft afternoon light streams through lace curtains. An elderly woman with silver hair is there arranging wildflowers.”Subject buried in description.

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Prompt Length

LengthWordsBest For
Short10-30Quick concepts, style exploration
Medium30-80Most production work
Long80-300+Complex editorial, detailed product shots
Longer prompts work well when every detail serves the image. Avoid filler — each sentence should add visual information.

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Style and Mood Annotations

Adding explicit style and mood descriptors at the end of your prompt can enhance consistency: 
[Scene description]. Style: Country chic meets luxury lifestyle editorial.
Mood: Serene, romantic, grounded.

[Scene description]. Shot on 35mm film (Kodak Portra 400) with shallow
depth of field—subject razor-sharp, background softly blurred.
Model on exercise ball in 1990s editorial style

1990s fashion editorial

Two bison in stylized modern room with blue walls

Surreal interior

Musician silhouette against glowing orange sunset

Golden hour silhouette

Silhouette figure against city skyline at dusk

Moody cityscape

Anime dragon in nocturnal forest with neon glow

Anime fantasy

Wolf wearing sheep costume, whimsical style

Whimsical illustration

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Image Editing

For image editing, prompts describe the transformation you want. Focus on what changes while letting the input image(s) provide the foundation.
Key principle: Reference images carry visual details. Your prompt describes what should change or how elements should combine—not what they look like.

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Single-Image Editing

Edit TypePrompt PatternExample
Style transfer”Turn into [style]""Reskin this into a realistic mountain vista”
Object swap”Replace [element] with [new element]""Replace the bike with a rearing black horse”
Element replacement”Replace [element] with [new element]""Replace all the feathers with rose petals”
Add elements”Add [element] to [location]""Add small goblins climbing the right wall”
Environmental”Change [aspect] to [new state]""Change the season to winter”
Original abstract artwork

Input

Mountain vista transformation

'Reskin this into a realistic mountain vista'

Person on motorcycle

Input

Person on rearing black horse

'Replace the bike with a rearing black horse'

Portrait with feathers

Input

Portrait with rose petals

'Replace all the feathers with rose petals'

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Multi-Reference Editing

Combine multiple input images for style transfer and complex edits. When using multiple references, specify the role of each.
Original portrait

Input image 1

Style reference portrait

Input image 2

Styled portrait with fluffy hair

'Change image 1 to match the style of image 2. Make the woman's hair just as fluffy'

Style reference image 1

Style reference 1

Style reference image 2

Style reference 2

Black Forest in combined style

'Image of the Black Forest. Use the style from the reference images.'

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Writing Effective Prompts

Be specific about what changes and clear about the target state. Reference image locations when needed (e.g., “image 1”, “image 2”) and let the base image provide context.

Good prompts

  • “Add dramatic storm clouds to the sky”
  • “Change her dress from blue to deep burgundy”
  • “Age this portrait by 30 years”
  • “Change image 1 to match the style of image 2”

Avoid

  • “Make it better”
  • “Improve the lighting”
  • “Make it more professional”
  • “Fix the image”

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Model Variants

VariantSpeedLicenseBest For
[klein] 4BSub-secondApache 2.0High-volume workflows, local deployment (~13GB VRAM)
[klein] 9BSub-secondFLUX Non-CommercialProduction work, best prompt understanding
Base 4B/9BStandardSame as aboveFine-tuning, research (undistilled, higher diversity)
Try [klein] via API — Get started in minutes with sub-second generation. No GPU required. View API docs →
API models (4B, 9B) are step-distilled for speed. Base variants preserve full training signal for customization.

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Best Practices Summary

Describe scenes as flowing paragraphs. “A weathered leather journal lies open on an oak desk, morning light revealing handwritten entries in faded ink” works better than “journal, leather, oak desk, morning light, handwriting.”
Put the most important element first. Word order signals priority to the model.
Specify light source, quality, direction, and how it interacts with surfaces. Lighting descriptions have the highest impact on output quality.
Include textures, reflections, and atmospheric elements. “Flaky croissant layers catching soft diffused light” is more evocative than “croissant on table.”
End prompts with explicit style or mood annotations when you want consistent aesthetic results across multiple generations.
When using reference images, describe relationships and context—let the images provide visual details.
For i2i editing, clearly state what should change and the target result. Avoid vague instructions.

Try [klein] via API

Sub-second generation from $0.014/image. No GPU required—start generating in minutes.

Download Weights

Run locally with open weights. 4B (Apache 2.0) or 9B (FLUX Non-Commercial).