AI image models: FLUX

AI image models, episode 1. Next: Google Nano Banana vs OpenAI GPT Image, then xAI Grok Imagine (image).

This series explains one or two AI image models per post, using the same fourteen questions every time. Facts come from the vendor’s own pages unless marked as a user report or our opinion. Prices were checked on 21 October 2026.

FLUX is made by Black Forest Labs (BFL). This episode covers two current models: FLUX 3 Image, released through BFL’s API on 1 October 2026, and FLUX 3 Image Klein, a 5.6-billion-parameter open-weights version released on 15 October (our Klein story).

What it does differently. FLUX 3 Image is built around precise control rather than one-shot prompting: up to 10 reference images, bounding boxes that say where each element goes on a 0 to 1000 grid, and local edits that BFL describes as pixel-exact outside the edited area. Klein brings the same feature set to a model that BFL says runs on consumer GPUs down to an RTX 3090. Grounding web search is on by default for FLUX 3 Image (BFL docs).

FLUX 3 Image and Klein against the checklist

1. Max resolution. Both go up to 4K, about 16 megapixels (BFL docs; one documented example is 5456 x 3072). Output sizes are 768 square, 1K (default), 1.5K, 2K and 4K.

2. Aspect ratios. FLUX 3 Image takes 15 fixed ratios from 21:9 to 9:21, or “auto”, which follows your first reference image (BFL docs). Klein’s full ratio list is not documented on the pages we read; its examples use ratios such as 4:3.

3. Reference types. Subject and object references, style references, instruction edits of an existing image, bounding-box placement, move, resize and remove, and multi-image composition (BFL docs). FLUX 3 Image takes no negative prompt; BFL says to describe what you want instead.

4. References at once. Up to 10 images for both models (BFL docs, Klein model card).

5. Price (per image, BFL API, checked 21 and 23 October). FLUX 3 Image: $0.041 at 768 square, $0.048 at 1K, $0.100 at 2K, $0.607 at 4K; the 1.5K price was not shown in the docs table we read. Klein: $0.008, $0.009, $0.011, $0.014 and $0.036 for 768, 1K, 1.5K, 2K and 4K. Editing costs the same as generation. BFL credits are $0.01 each, and API and Playground prices match. Klein weights are free to download under its licence (see item 13).

6. Speed and rank. BFL says a 4K FLUX 3 Image “can take several minutes”; other generation times are not published. For Klein, BFL says the distilled model with its INT8 build makes a 1-megapixel image in about 4 seconds on an RTX 5090 and under 9 seconds on an RTX 4070. On the Artificial Analysis text-to-image leaderboard (rechecked 23 October) FLUX 3 Image is #13 with an Elo of 1117; the leader, GPT Image 2.5 Sunburst, has 1222. Klein now appears at #21 with 1043, within the ±12 margin of Qwen-Image-2.1 (1042) and Fibo 2.0 (1039).

7. Character consistency. Done with references: BFL’s multi-reference guide shows feeding the same character image to “keep a character consistent across variations”. There is no separate identity-lock feature.

8. Style and scene consistency. Style references and fixed layouts via bounding boxes; BFL documents style and mood tags for consistent looks. Nothing beyond reference reuse is documented for series work.

9. Compared with the previous version. FLUX.2 [max] and [pro] rank #35 and #44 on the same Artificial Analysis board, so FLUX 3 Image is a large jump there. BFL says Klein gains 91 Elo in text-to-image and 70 in editing over FLUX.2 [klein] 9B in its internal evaluations, with 38% fewer parameters. FLUX.2 remains supported.

10. Text in images. BFL documents single words, multi-line poster typography and Japanese text, with each text block quoted in the prompt.

11. What users think (user reports, not facts).

• Praise: @tomislav_rupic likes Klein Base but says 2K at 50 steps took about 13 minutes on an M3 Ultra. @SeaArt_Ai, a platform hosting it, highlights box edits and clean in-image text.
• Complaints: @deeperflows was “extremely disappointed” with Klein renders; @yunqalus says it “clearly struggles with human anatomy”; @n1d_all says it has weak world knowledge; @VisualInference wrote about its “wax faces”. @flowersslop summed up the mood as “people seem pretty disappointed with flux 3 klein”. Most early complaints are about Klein, not FLUX 3 Image.

12. General quality. We have not generated FLUX images for this series yet. The leaderboard rank says FLUX 3 Image holds up in blind votes, while Klein sits mid-table; user complaints focus on Klein’s faces and anatomy. BFL’s FLUX 3 Image page is its official gallery.

13. Licence, commercial use, open weights. Under BFL’s developer terms, you own API output and may use it commercially; BFL may embed Content Credentials. FLUX 3 Image has no public weights (a commercial weights licence is available through BFL sales). Klein’s weights are under the FLUX Kommunity License: non-commercial use, plus free commercial output for users with under $5 million in annual revenue (model card); larger companies need a paid licence or the API.

14. Our verdict (opinion). Pick FLUX 3 Image if you edit and compose more than you prompt from scratch: 10 references and box placement are the standout tools. Pick Klein if you need a model you can run and fine-tune yourself for about a cent an image via API. Skip Klein for photoreal people until the face and anatomy complaints are answered.

FLUX 3 video, briefly: BFL also sells video models. FLUX 3 Max is #4 and FLUX 3 #7 on the Artificial Analysis text-to-video board (21 October); see our FLUX 3 Max story. They belong in the movie series wrap-up.

Summary

#	Checklist	FLUX 3 Image	FLUX 3 Image Klein
1	Max resolution	4K (~16 MP)	4K
2	Aspect ratios	15 fixed, 21:9 to 9:21, plus auto	not documented
3	Reference types	subject, style, edit, boxes, multi-image	same
4	References at once	10	10
5	Price (21 Oct)	$0.041 to $0.607 per image	$0.008 to $0.036; weights free under licence
6	Speed, rank	4K “several minutes”; AA #13 (1117)	~4 s 1 MP on RTX 5090 (BFL); AA #21 (1043)
7	Character consistency	via references	via references
8	Style/scene consistency	style refs, boxes	same
9	vs previous	far above FLUX.2 on AA	+91 Elo vs FLUX.2 klein 9B (BFL)
10	Text rendering	multi-line, Japanese (BFL)	typography examples (BFL)
11	Users	few reports	faces and anatomy complaints
12	Quality	strong blind-vote rank	mixed early reviews
13	Licence	you own output; closed weights	Kommunity licence, free commercial under $5M
14	Verdict (opinion)	editing and composition	local and fine-tuning