If black borders appear only when proxies are enabled in DaVinci Resolve, compare the same frame with camera originals, then check the proxy’s dimensions and framing. Regenerate a mismatched proxy before changing your edit’s zoom or crop.

This guide is for a Mac editor whose original footage looks correct but changes size or gains borders during proxy playback. The Resolve instructions follow Blackmagic Design’s 21.1 reference manual; the final sections cover relevant Fusion, Premiere, and Final Cut Pro differences.

Confirm that switching media causes the borders

Start with one affected clip at a frame containing clear details near its edges. Keep the playhead, viewer magnification, and clip adjustments unchanged throughout the comparison. This makes the test useful: you are checking whether the media switch changes the picture.

  1. On Resolve’s Edit page, choose Playback → Proxy Handling → Disable All Proxies.
  2. Check whether the original picture has the expected framing.
  3. Switch to Prefer Proxies and compare the same frame.
  4. Return to Disable All Proxies before making framing decisions.

Use Disable All Proxies for this test because Prefer Camera Originals can fall back to proxies when originals are unavailable. Disabling proxies forces original-media playback; an unavailable original produces a Media Offline graphic. These playback choices are documented in Chapter 8 of the DaVinci Resolve 21.1 Reference Manual.

Interpret the comparison before changing anything:

Result Next action
Originals look correct; proxies gain borders Inspect the linked proxy and regenerate one test clip.
Both versions show the same borders Check source-to-timeline aspect ratio and scaling.
Originals are offline Reconnect them before judging whether the problem is exclusive to proxies.
Only a Fusion preview changes Check Fusion’s separate preview controls.

This is a diagnostic sequence derived from the documented controls, rather than proof of one universal cause. A proxy file with padding, an unexpected proxy attachment, and a composition preview issue require different corrections.

Check the actual proxy file and its proportions

In the Media Pool, switch to list view. Right-click a column heading and enable Proxy and Proxy Media Path. The first column shows proxy status or its online resolution; the second identifies the file location Resolve expects. Use that path to inspect the proxy actually attached to the affected clip. DaVinci Resolve manual, Chapter 8.

Compare the source and proxy dimensions, orientation, and visible picture boundaries. If necessary, import the proxy into a separate test project as ordinary media so you can inspect its own frame. Borders visible inside that file’s picture area point to padding already encoded into the proxy. Matching dimensions alone do not establish matching framing: a file can contain black pixels around a smaller image.

Use proportional dimensions as a first check

For square-pixel footage without a rotation difference, reducing width and height by the same factor preserves the frame’s proportions. These illustrative calculations show why a generic HD preset may be unsuitable for some sources:

Original dimensions Reduction Proportional proxy dimensions
3840 × 2160 Half 1920 × 1080
4096 × 2160 Half 2048 × 1080
4096 × 2160 Quarter 1024 × 540
6144 × 3456 Quarter 1536 × 864
2160 × 3840 Half 1080 × 1920

Consider a synthetic 4096 × 2160 graphic fitted proportionally into a 1920 × 1080 proxy. Its calculated picture height is 1920 × 2160 ÷ 4096 = 1012.5 pixels, leaving about 67.5 pixels of total vertical padding before encoder rounding. A 2048 × 1080 proxy preserves the original proportions without that particular mismatch. This illustrates the geometry; it does not predict every encoder’s output.

For anamorphic or non-square-pixel footage, also check pixel aspect ratio. Adobe distinguishes frame aspect ratio from pixel aspect ratio and advises resolving pixel-aspect interpretation before frame-aspect problems. A squeezed picture needs an interpretation check before a crop decision. Adobe: Aspect ratios.

Regenerate one Resolve proxy before replacing the whole batch

Resolve provides source-relative proxy sizes, making an explicit Half or Quarter setting a useful controlled test. In Project Settings, open Master Settings and find Optimized Media and Render Cache. Set Proxy media resolution to the chosen reduction and select an available Proxy media format, such as a ProRes proxy option. These settings govern files created by Generate Proxy Media. DaVinci Resolve manual, Chapter 8.

  1. Select one affected source clip in the Media Pool.
  2. Right-click it and choose Generate Proxy Media.
  3. Wait for generation to finish.
  4. Check the resulting Proxy resolution and Proxy Media Path.
  5. Repeat the same-frame comparison between Disable All Proxies and Prefer Proxies.
  6. If framing now matches, regenerate the remaining affected clips with the tested settings.

Changing the project setting alone does not replace an existing proxy. Resolve’s documented regeneration procedure creates another file, appends an _s00x suffix, and automatically links the latest generated proxy. Earlier versions remain on disk, allowing you to keep them until the replacement has been checked. DaVinci Resolve manual, “Re-generating Proxy Media”.

The Choose Automatically setting is based on timeline resolution: Resolve reduces sources larger than the timeline using a suitable reduction ratio. An explicit size makes the troubleshooting test easier to interpret, but it is not a documented cure for every border problem.

Keep the free-version boundary precise

Blackmagic’s Resolve 21.1.1 release notes state that the free edition can handle unlimited-resolution source media while limiting project mastering and output to Ultra HD or lower. That statement does not establish that every oversized source creates letterboxed proxies. Check the generated file rather than assuming the edition explains its borders. Blackmagic Design: About DaVinci Resolve 21.

If a particular size or format cannot be generated in your installation, try a smaller proportional proxy in a supported codec. For externally generated proxies, Resolve requires matching timecode, matching filename excluding the extension, matching frame rate, and a supported format and codec. Select the original clips, right-click, choose Link Proxy Media, and locate the replacement files. Successful attachment still needs a visual framing check. DaVinci Resolve manual, Chapter 8.

Change image scaling only when the originals need it too

If borders remain with proxies disabled, inspect Project Settings → Image Scaling → Input Scaling → Mismatched resolution files. Resolve documents distinct behaviors:

Setting Effect
Scale entire image to fit Preserves the whole picture and adds blanking where the proportions differ.
Scale full frame with crop Fills the frame and crops excess picture.
Center crop with no resizing Leaves the image unscaled; smaller images receive surrounding blanking and larger images are cropped.
Stretch frame to all corners Fits both dimensions by stretching or squeezing the picture.

DaVinci Resolve manual, Chapter 11.

Choose according to the intended composition. Keeping the entire image can legitimately leave bars when source and timeline proportions differ. Filling the frame sacrifices image content. Stretching changes proportions. Because these are project-level choices, record the existing setting and assess other clips before adopting a change.

When the original already looks correct, leave its framing intact while replacing the problematic proxy. Zooming the timeline clip to hide proxy padding can crop the correctly framed original when playback switches back. That consequence follows from applying a composition change to compensate for a different representation of the same clip.

Distinguish proxy files from Fusion and timeline previews

Resolve’s timeline proxy processing reduces working resolution on the fly; generated proxy media consists of separate files on disk. Blackmagic explicitly describes these as independent features. Changing the timeline preview resolution therefore does not regenerate a padded proxy file. DaVinci Resolve manual, Chapter 8.

Fusion also has separate Proxy and Auto Proxy preview controls. Proxy reduces interactive processing resolution, while Auto Proxy temporarily reduces resolution during adjustments and restores it when the control is released. The Fusion manual distinguishes enabling Proxy through the transport-area context menu on Resolve’s Fusion page from using the Prx button in standalone Fusion Studio. Fusion 21.1 Reference Manual, Chapters 2–3.

If the issue appears only in a Fusion preview, compare with its preview proxy control disabled before rebuilding media. If switching Resolve’s linked media changes an ordinary clip on the Edit page, continue with the proxy-file checks above. This keeps similarly named controls from sending the investigation in the wrong direction.

Apply the same framing test in Premiere or Final Cut Pro

In Premiere on Mac, Adobe’s current documented creation path is to right-click eligible online video in the Project panel and choose Proxy → Create Proxies. The defaults are Half frame size and ProRes QuickTime Proxy; Adobe Media Encoder processes the jobs. Test a replacement created from the original instead of repeating a fixed-size preset that produced unexpected padding. Adobe: Create proxies.

Keep that advice within Adobe’s supported workflow: its proxy documentation lists footage interpretation changes as unsupported and says Premiere’s proxy functionality is incompatible with After Effects’ proxy functionality. Do not rely on changing interpretation midway through an attached-proxy workflow to repair the mismatch. Adobe: Ingest and Proxy workflow.

In Final Cut Pro, use the viewer’s View menu and compare Optimized/Original with Proxy Only. Proxy Preferred can fall back to optimized or original media, which makes it less conclusive for this test. Apple’s current guide identifies ProRes 422 Proxy and HEVC as proxy formats and instructs editors to return to Optimized/Original before sharing. These are Final Cut controls, separate from Resolve’s proxy system. Apple: Control playback quality in Final Cut Pro for Mac.

Verify the final output from originals

In Resolve, finish by disabling proxies and reviewing the corrected section. On the Deliver page, leave Use proxy media unchecked in the video render settings’ Advanced Settings when you want original-source output. Resolve normally returns to source media for delivery; enabling that option overrides the behavior. Originals must be available for the intended original-media render. DaVinci Resolve manual, “Using Proxy Files for Delivery”.

Render a short representative section and inspect its picture edges, composition, and output dimensions. The repair is complete when the replacement proxy preserves the intended framing during editing and the original-media export preserves it too. If borders persist only in a composition or one source format, retain the same-frame comparison results and investigate that narrower case before changing the whole timeline.

Sources