Pick 9:16 before you generate
Set 9:16 before you generate. Cropping a 16:9 hero for TikTok is a new crop, not a vertical shot.
Pick 9:16 before you generate if the clip is for TikTok, Reels, or Shorts. Cropping a 16:9 hero after the fact is a new crop. It is not a vertical shot. You will lose the hands, the label, or the head, and you will not get them back by prompting “phone video” on a file that was already framed for a television.
This week’s radio is the aspect control on the generate, not a recrop in the editor. Editors crop. They cannot invent the pixels that 16:9 never rendered at the top and bottom of a 9:16 frame.
The generate has a shape. Honour it.
Most video rows expose aspect as a listed option: 16:9, 9:16, sometimes 1:1, 4:3, 21:9, auto. Gemini Omni Video lists 16:9 or 9:16 at 4–10 seconds. Veo 3.1 is a generate you should still set to the ratio you will ship. The AI video generator will not silently deliver a TikTok-safe frame because the caption mentioned TikTok.
9:16 is 1080×1920 thinking: a tall window. Faces sit in the upper third. Product sits large in the middle. Captions and overlays must clear the safe area at the bottom. 16:9 is a wide window. The same composition, cropped to 9:16, becomes a slice through the middle of a room. The pack that was nicely tabled in landscape is now a floating label with no table, or a table with no pack.
I2V inherits this twice. If the still is 16:9 and the video row will follow the still, you are generating a landscape clip whether you wanted TikTok or not. Crop the still to 9:16 before you attach it. Writing “9:16” in the prompt does not recrop a 16:9 pack shot. Recrop, then generate.
T2V will invent a composition that fits the aspect you selected. If you selected 16:9, it will invent a wide blocking: two people on a couch, a horizon, a car in profile. Verticalizing that after the fact is how you cut the second person off. Generate 9:16 and the model will stack the blocking for a phone.
1:1 and 4:5 are not 9:16. A 4:5 hero for Instagram feed is a different radio from a Reels 9:16. If this week’s destinations include both, you owe two generates or a still that can crop both without killing the SKU. You do not owe one 16:9 master and a prayer.
Cropping a 16:9 hero is a different job
Post-crop is valid when the 16:9 file was always the master — a YouTube long-form, a course, a landscape ad — and you are making a clip that can survive a centre crop. It is not valid as a plan for a talking-head TikTok you have not generated yet.
What a 16:9→9:16 crop actually does:
- Keeps a vertical strip. Usually the centre, unless you keyframe the crop.
- Throws away left and right. Hands on a table, product flanks, the second speaker in a two-shot.
- Does not add headroom. If the landscape shot was a medium-wide, the vertical slice may still miss the hair and the label at the same time.
- Moves every safe-area assumption. Captions burned for 16:9 sit in the wrong place on 9:16 chrome.
If you already generated 16:9 by mistake this week, do not burn captions on it and then crop. Crop first (or regenerate at 9:16), then caption. Burned type in the lower-third of a landscape frame will sit in the middle of a vertical frame, or vanish into the cut.
Reframing with an edit model is still not a 9:16 generate. You can ask an editor to punch in. You cannot ask it to restore a forehead that was never in the raster. If the hero must be vertical and the landscape take does not contain a usable strip, regenerate.
Platform UI is why this radio exists. TikTok, Reels, and Shorts draw usernames, buttons, and sometimes auto-captions on the lower portion of 9:16. A landscape crop that “sort of fits” still puts your hook under that chrome. Generate 9:16, leave the lower band quiet, put burned-in captions where a phone can read them.
This week’s destinations, this week’s ratio
Write the destination before the prompt:
| This week’s post | Aspect to generate | Do not |
|---|---|---|
| TikTok, Reels, Shorts | 9:16 | Crop a 16:9 hero and hope |
| YouTube long-form, course | 16:9 (or the player’s ratio) | Force 9:16 and letterbox |
| Same story in both | Two files, or a still that crops cleanly both ways | One generate, two crops as the plan |
If the week is only vertical, set 9:16 on every generate, including drafts. Drafts in 16:9 teach you a blocking you will throw away.
If the still is a pack shot from the website (usually landscape), recrop the pack for 9:16 so the label is large and centred, then I2V. Do not I2V the website still and crop the motion. Motion cropped off a label is a smear.
Thumbnails are a still job at the size the platform serves. A 9:16 generate is the wrong aspect for a 16:9 YouTube poster. Do not reverse the radio either: do not generate 16:9 “for the thumbnail” and then try to post that file as a Short.
Audio does not change aspect. Native audio on a 16:9 talking shot is still a landscape talking shot. You will crop the mouth. Pick 9:16, then pick the sounded row.
The Monday radio
- List destinations. If any of them are TikTok / Reels / Shorts, those clips generate 9:16.
- Crop stills to 9:16 before I2V.
- Set the aspect control on the model card before you write the prompt. The prompt should describe a tall frame, not a wide one.
- Preview on a phone. If you are watching a 16:9 file in a vertical player with black bars, you missed the radio.
- Caption after the ratio is locked.
A second generate at the right ratio is cheaper than a week of ads pointing at a cropped forehead. The editor is for trims, not for inventing 9:16.
If you need to run the same brief at 9:16 and 16:9 as two jobs, sign up and set the ratio before the first credit. Vertical is a generate setting. It is not a crop preset.
FAQ
Can I generate 16:9 and outpaint to 9:16?
Outpaint is a new generate of the missing bands. Identity at the edges is invented. For a SKU or a face you already approved, that is a cousin. Prefer a native 9:16 generate or a still already cropped to 9:16.
The model card says “auto.” What does that do?
Auto usually follows the still or a default landscape. Do not use auto for a TikTok you have not framed. Set 9:16 explicitly. If the row has no 9:16 option, pick a row that does, or crop a still and use I2V on a row that inherits the still.
We need both a Short and a 16:9 end card from one hero.
Generate the hero at 9:16 for the Short. Pull a still for the end card and extend canvas or generate a 16:9 poster from that still. Do not treat a centre crop of 16:9 as the Short and the full frame as the poster unless you already checked that the crop contains a complete face and a complete label.