You generated a 16:9 clip in Runway and exported a 9:16 vertical for TikTok or Reels. The platform’s auto-crop took the center column, and now the subject’s head is sliced off, or the two people in the wide shot are each framed half-off-screen. The clip is unusable on the target platform without manual re-framing.
Fastest fix: if you can still regenerate, set the aspect ratio to the target before generating. Native vertical always beats post-crop. If you cannot regenerate (the clip is final, or credits matter), use a subject-tracking reframe instead of a center crop: Sequence > Auto Reframe Sequence in Premiere Pro, or Smart Reframe in DaVinci Resolve Studio. Both follow the subject across the frame instead of blindly keeping the center column. Smart bars (blurred or solid) are the last resort when a single crop cannot hold the composition.
Which bucket are you in?
Match your symptom to the cause, then jump to the matching step.
| Symptom | Likely cause | Go to |
|---|---|---|
| Head/face clipped, subject was off-center | Center-crop on an off-center composition | Step 3 |
| Two subjects each half-cut | One crop cannot hold both | Step 4 |
| Subject fine at start, empty space at end | Subject moves during the clip | Step 3 / Step 5 |
| Whole frame stretched or squashed | Wrong sequence/export size | Step 1 / verify section |
| Black bars framed into the new crop | Letterbox baked into source | Step 6 |
| Vertical version looks softer than horizontal | Tool’s vertical mode renders lower res | Step 1 |
Common causes
Ordered by hit rate.
1. Generated at one aspect, delivering to another
Runway Gen-4 / Gen-4.5 default output is 16:9 at 1280x720 (720p). TikTok wants 9:16 at 1080x1920. Cropping a 16:9 frame to 9:16 keeps only the center ~28 percent of the width, which clips the subject whenever it was anywhere off-center.
How to spot it: source aspect ratio differs from delivery aspect ratio.
2. Tool’s vertical mode produces lower quality
Some pipelines generate vertical clips at lower internal resolution than the horizontal equivalent. With Sora 2, for example, standard 9:16 output is 720x1280 (720p); the higher-res 1024x1792 portrait (up to 1080p) is a Sora 2 Pro option (as of June 2026). Composition can be fine while detail lags the horizontal render, so a vertical version can look softer for reasons that have nothing to do with your crop.
How to spot it: generate the same prompt in both ratios. If vertical looks visibly softer, the tool’s vertical mode is the limiter, not your crop.
3. Center-crop assumption when subject is off-center
Composition put the subject on the rule-of-thirds, but auto-crop assumes center. The subject ends up at the edge or fully cropped.
How to spot it: Pause the source clip; if subject’s eyes are not on the vertical center line, center-crop will misframe.
4. Letterbox bars baked into the source
Source clip has black bars top and bottom from a previous step. Re-crop ignores the bars and frames partially on black.
How to spot it: Inspect the source clip; if there are visible bars, they need to be cropped out before re-frame.
5. Animated subject moves out of center during the clip
Subject starts centered then walks left. Static center-crop captures the empty right side at the end of the clip.
How to spot it: Watch the source; if subject moves significantly, no static crop will work.
6. Wrong aspect set in delivery tool
Premiere sequence is 1920x1080 but you exported to 1080x1920 — the sequence math is wrong and the export comes out stretched or with bars.
How to spot it: Check sequence settings match delivery target.
Before you start
- Save the original generated clip at full quality.
- Identify the source aspect and the target aspect.
- Determine if subject is centered, off-center, or moves during the clip.
- Decide whether to regenerate at target aspect or to re-frame the existing clip.
- Note the target platform’s exact resolution (TikTok 1080x1920, Reels 1080x1920, YouTube Shorts 1080x1920, Square 1080x1080).
Information to collect
- Source clip resolution, fps, and aspect.
- Target platform resolution and aspect.
- Subject position (centered, left third, right third, moving).
- Whether the source has letterbox bars.
- The delivery tool (CapCut, Premiere, Resolve, FCPX, native platform editor).
Step-by-step fix
Step 1: Generate natively at the target aspect when possible
Native vertical generation at the target ratio always beats post-crop, because the model composes for the frame it is given. Set the ratio in the generation panel before you hit generate, not after. Tool support as of June 2026:
# Runway Gen-4 / Gen-4.5
- Supports 16:9, 9:16, 4:3, 3:4, and 1:1
- Default 720p (1280x720); "Upscale to 4K" button appears beneath a finished
generation on paid plans
- Set aspect ratio + resolution in the settings panel before generating
# Pika 2.5
- Supports 16:9, 9:16, 1:1, 4:5, 5:4, 3:2, 2:3 (7 ratios)
- Aspect ratio dropdown in the generation panel
# Kling 2.5 Turbo / 2.6
- Supports 16:9, 9:16, 1:1
- Up to 1080p; pick ratio before generating
# Sora 2 (OpenAI) — consumer app/web discontinued
- Note: OpenAI discontinued the Sora web and app experiences (sora.com plus the
iOS/Android apps) on April 26 2026, and the Sora API is set to shut down
Sep 24 2026 (as of June 2026). If you previously generated here, you can no
longer pick a Sora ratio in-app; generate vertical in Runway, Pika, or Kling
instead, or reframe an existing Sora clip with Steps 3-7
- For reference, Sora 2 supported 16:9 and 9:16; standard 9:16 portrait was
720x1280 (720p), with Sora 2 Pro adding a higher-res 1024x1792 portrait
(up to 1080p)If your tool/version is not listed, the rule is the same: choose the ratio in the panel before generating. Only fall back to cropping when the source is already final.
Step 2: Compose for the most restrictive aspect first
If you must deliver in multiple ratios:
- Generate 9:16 first (most restrictive vertical)
- Subject in the top two-thirds, never the bottom
- Center the face vertically at 40 percent from top
- Generate 16:9 separately with wider composition
- Do not assume a single generation will work in bothStep 3: Reframe with subject tracking (Premiere or DaVinci)
Subject-tracking reframe follows the detected subject across the frame instead of holding the center column, so an off-center or slowly moving subject stays in shot.
# Premiere Pro
- Whole timeline: select the sequence in the Project panel, then
Sequence -> Auto Reframe Sequence. This creates a duplicate sequence at the
target ratio; the dialog now lets you set the Target Aspect Ratio AND the
target resolution (e.g. 1080x1920) directly, so you no longer have to fix
sequence settings by hand afterward (as of June 2026)
- Single clip: drop the Auto Reframe effect (Video Effects -> Transform ->
Auto Reframe) onto the clip, or open a target-ratio sequence and add it
- Motion Tracking preset (in the dialog / Effect Controls): Slower Motion,
Default, or Faster Motion
- Talking head / interview (little camera motion): Slower Motion
- Walking / general action: Default
- Sports / fast action: Faster Motion (adds the most keyframes)
# DaVinci Resolve Studio (Smart Reframe is Studio-only; Studio is a
# one-time $295 license, as of June 2026 — the free version has no Smart Reframe)
- Put the clip in a project/timeline at the target ratio
- Inspector -> Sizing (or Transform) -> Smart Reframe
- Object of Interest: Auto (Neural Engine picks the main subject and can run
across multiple clips at once) or Reference Point. For Reference Point,
pick it from the dropdown, click the Target icon to its right, then drag the
crosshair onto the subject you want tracked
- Reference Point must be set per clip; Auto applies across clips
- Smart Reframe also tracks products, props, pets, and wildlife, not just facesBoth follow the detected subject and beat a static center-crop in the large majority of cases. They are weakest with two equally important subjects or a subject that fully leaves frame; see Step 4 and Step 5.
Step 4: Add smart bars when re-frame is not possible
For two people side-by-side in a 16:9 needing 9:16 delivery:
# Option A: Blurred bars
- Resize to fill width at 9:16
- Background: same clip, scaled to fill height, blurred 50 px
- Foreground: original at full width, vertically centered
# Option B: Solid bars
- Less polished but cleaner for product / text content
- Top and bottom bars in brand color
# Option C: Hero crop
- Pick the most important person, center on them
- Other subject is sacrificedStep 5: Re-frame manually with keyframes
For moving subjects:
# Premiere
- Place clip in target-aspect sequence
- Effect Controls -> Position
- At t=0, position so subject is centered
- At every shot where subject moves > 10 percent of frame width, add a keyframe
- Use Bezier easing between keyframes10 to 20 keyframes for a 10-second clip is normal.
Step 6: Crop letterbox bars first if present
# ffmpeg crop black bars
ffmpeg -i input.mp4 -vf "crop=in_w:in_h-2*60:0:60" -c:a copy cropped.mp4Where 60 is the bar height in pixels. Use ffprobe and cropdetect to find the right value:
ffmpeg -i input.mp4 -vf "cropdetect=24:16:0" -t 5 -f null -The output suggests a crop value.
Step 7: Verify on the actual target platform
Each platform overlays UI (caption, follow button, like/comment/share column) on top of your video, so a frame that looks fine in your editor can still have the face or text hidden behind chrome. Keep important content inside the safe zone. Approximate safe-zone margins in a 1080x1920 frame, as of June 2026:
- Upload to TikTok / Reels / Shorts as a draft and preview in-app
- TikTok (organic): keep content clear of
top ~140 px (profile bar / notch / Dynamic Island),
bottom ~324 px (caption + sound attribution + CTA),
right ~164 px (like/comment/share/bookmark column)
TikTok Ads (Spark / In-Feed) push the bottom margin to ~370 px for the
CTA button (Shop Now, Learn More)
- Instagram Reels: no faces/text/CTAs in the bottom ~310 px,
keep the right column clear for action buttons
- A universal multi-platform safe area is roughly the centered 960x1386 boxThese overlays move with app redesigns; if a number feels off, trust the in-app draft preview over a fixed pixel value.
Verify
- Open delivery file at native resolution; subject should be fully visible.
- Play through; subject should not drift toward an edge.
- Test on the actual target platform before finalizing.
- Three different reviewers should not flag composition issues.
Long-term prevention
- Decide target aspect before generating, not after.
- Build a project-level “vertical first” policy if delivery is mostly vertical.
- Standardize subject positioning: face at 40 percent from top for vertical, rule-of-thirds for horizontal.
- Always generate at native aspect ratio when the tool supports it.
- Keep a Premiere Auto Reframe preset library for common conversions.
Common pitfalls
- Center-cropping a rule-of-thirds composition.
- Assuming the platform’s auto-crop is smart enough to track the subject.
- Forgetting safe zones for captions and UI on TikTok / Reels.
- Re-encoding through multiple aspect changes; each step loses quality.
FAQ
Can I just regenerate at the new ratio? Yes, and it is usually the best option. Native generation at the target aspect always beats post-crop because the model composes for that frame. Set the ratio in the generation panel before generating.
Premiere vs DaVinci for reframing — which one? Premiere’s Sequence > Auto Reframe Sequence is fastest for whole timelines and ships with the standard app. DaVinci’s Smart Reframe tends to track better on tricky subjects but requires Resolve Studio (~$295 one-time, as of June 2026), not the free version. If you only have free Resolve, you do not have Smart Reframe.
Why is auto-reframe not perfect? Both Premiere and DaVinci use subject tracking. If the subject fully leaves frame, or there are two equally important subjects, the tracker picks one and can switch mid-clip. For those cases, hero-crop one subject (Step 4) or keyframe the position manually (Step 5).
Is blurred-bar fill considered low quality? TikTok and Reels viewers tolerate it for repurposed content, and it preserves the full original composition. For new, native content, shoot or generate vertical instead.
Why does my export look stretched instead of cropped? That is a sequence/export size mismatch, not a crop problem. Your sequence aspect must match the delivery target (for example a 1080x1920 sequence for 9:16). Check the verify section.
Related
- AI video camera jitter fix
- AI video frame flicker fix
- AI video export black frames
- AI video too static
- AI video scene inconsistency
External references: