21:9 ultrawide AI video API: which Sume models accept it
Seedance 2.5, Seedance 2 and its variants, MiniMax H3 and H3 Max accept aspect_ratio 21:9 on Sume. Wan 3.0, Kling 3 and Gemini Omni Flash do not.
Seedance 2.5, Seedance 2, 2 Fast and 2 Mini, MiniMax H3 and MiniMax H3 Max list 21:9 in their supported aspect ratios on Sume. Wan 3.0 (16:9, 4:3, 1:1, 3:4, 9:16), Kling 3 (16:9, 9:16, 1:1) and Gemini Omni Flash 1.1 (16:9, 9:16) do not. Pass aspect_ratio as 21:9 only to a model that lists it.
Aspect ratios by model (read 2026-10-04)
Source: the Sume video catalog.
| Model | 21:9 | Other ratios |
|---|---|---|
| seedance-2.5, seedance-2, 2-fast, 2-mini | Yes | auto, adaptive, 16:9, 4:3, 1:1, 3:4, 9:16 |
| minimax-h3, minimax-h3-max | Yes | adaptive, 16:9, 4:3, 1:1, 3:4, 9:16 |
| wan-3.0 | No | auto, adaptive, 16:9, 4:3, 1:1, 3:4, 9:16 |
| kling-3 | No | 16:9, 9:16, 1:1 |
| gemini-omni-flash-1.1 | No | 16:9, 9:16 |
| grok-imagine-video-1.5, genjutsu, h3-max-recast | No aspect_ratio option | none |
A 21:9 request
This asks for a cinematic wide frame from Seedance 2.5 at 1080p.
curl -X POST "https://api.sume.com/v1/videos" \
-H "Authorization: Bearer $SUME_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "seedance-2.5",
"prompt": "A train crosses a canyon bridge, anamorphic look",
"duration": 8,
"resolution": "1080p",
"aspect_ratio": "21:9"
}'What if you need 21:9 from a model without it
Render at the widest supported ratio, 16:9, and crop to 21:9 afterwards with the video filter. That throws away part of the frame, so frame your prompt with the crop in mind.
Lengths and resolutions for the 21:9 models
Seedance 2.5 runs 4 to 30 seconds and Seedance 2 and its variants 4 to 15, all at 480p, 720p and 1080p. MiniMax H3 runs 5 to 15 seconds at native 480p and 768p, and H3 Max adds 1080p. Pick on length first.
Sources
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Written by Sume