AI image for Instagram 4:5 (1080×1350): what the API returns

Send aspect_ratio: "4:5" to POST /v1/images. Sume's docs are explicit that 4:5 is Instagram portrait (1080×1350), not 4:3. A model returns its native size for that ratio: Nano Banana Pro renders about 928×1152 at 1K, and exact 1080×1350 is a post-step through job target_pixels, not a native output.

Read from the Image API and Image 1.0 docs on 2026-09-29. Google's docs list 4:5 among the ratios its Nano Banana models support.

How do I request a 4:5 image?

aspect_ratio is a normalized ratio. Read supported_parameters on the model before pinning it, because a model accepts only the values its catalog lists and anything else returns 400 unsupported_parameter.

curl -X POST https://api.sume.com/v1/images \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "google/nano-banana-pro",
    "prompt": "Flat-lay of a linen shirt, a straw hat and sunglasses on sand",
    "aspect_ratio": "4:5",
    "resolution": "2K"
  }'

Will the file be exactly 1080×1350?

Not from Nano Banana. Sume's docs say a WIDTHxHEIGHT value on Nano Banana maps to the native ratio (1080×1350 becomes 4:5), and exact pixels are a documented post-step. The GPT models cannot use 1080 either: the docs say custom GPT edges must be multiples of 16, and 1080 is not one, so 4:5 there expands to 1024×1280 (per the API reference).

What if I need the exact pixel size?

Ask for 4:5 at the highest tier your budget allows, then resize to 1080×1350 in your own step. Sume's Image Upscale 1.0 posts cover the upscale side.

Does the wrong ratio crop my image?

That depends on where you post it, and this post does not state Instagram's cropping rules. Generate the ratio you plan to publish so no crop is needed.