Crop

Crop is a transform tool for changing image bounds rather than scaling image content. A normal 2D Image enters and a normal 2D Image leaves, but the output Width/Height and bounds may be different.

Blackmagic describes Crop as a tool that can cut out part of an image or offset the image into a larger image area. Crop therefore does more than remove edges: X/Y Size may be smaller or larger than the input resolution.

The first essential distinction is Crop versus Resize. Crop changes the canvas/output resolution and selected area without resampling the source pixels. Resize resamples content to different dimensions. They can look similar in a Viewer while behaving very differently downstream.

The second distinction is Crop versus Transform. Transform changes placement and scale inside an existing frame; Crop changes the frame itself. Moving a logo inside a finished 1920x1080 canvas is normally a Transform task, not an X/Y Offset Crop task.

X Size and Y Size are pixel values that define the horizontal and vertical resolution of Crop.Output. Downstream tools receive those physical image-stream dimensions.

X Offset and Y Offset are also pixel values. In the classic Fusion reference they position the top-left corner of the crop window relative to the source, so they choose which source area falls inside the new canvas rather than behaving like normalized Transform Center controls.

When X/Y Size are smaller than the input, Crop cuts out a rectangular region. When Size is larger, Crop creates additional canvas around the source and Offset determines source placement inside that larger area.

Reset Size restores the output dimensions to the input-image dimensions. Reset Offset independently restores X/Y Offset defaults; one reset does not imply the other.

Keep Aspect links X/Y Size changes to preserve the input-image aspect ratio. It is not Fit/Fill and does not scale the content into the new frame.

Keep Centered automatically adjusts offsets while Size changes so the crop window remains centered. Decide whether that behavior is wanted before manually tuning Offset, otherwise two control layers appear to fight each other.

Change Pixel Aspect concerns pixel shape, not ordinary Width:Height frame aspect. Historical Blackmagic documentation says enabling it reveals a Pixel Aspect control. The bundled current capture verifies the switch but not the expanded conditional UI, so target-build verification remains required.

Clipping Mode concerns Domain of Definition, the technical data region passed between Fusion tools and used during processing. It is not another visual crop rectangle.

The bundled current Crop Inspector shows None and Frame. Historical official Fusion documentation also describes Domain. This article therefore does not promise Domain as a current Resolve 21/21.1 menu choice without live verification.

In the classic description, Frame establishes the full output frame as the tool DoD; when upstream DoD is smaller, the remainder of the frame is treated as empty/transparent.

None disables normal source clipping for DoD processing. It does not remove output Width/Height; it changes how data outside the active upstream region is handled, which can matter for spatial filters such as Blur and Glow.

DoD matters because some downstream tools require neighboring pixels outside the current active region. An early Crop plus unsuitable clipping can cut soft effects even when the visible rectangle itself looks correct.

Auto Crop is a separate Inspector tab. R, G, B and A choose the channels evaluated when calculating useful bounds; disabled channels are ignored.

Auto Crop attempts to determine the background color and trims each side to the first pixel that differs from that background. This is pixel analysis, not semantic object segmentation.

For transparent PNG, Text+ or render-pass material, Alpha is often the cleanest coverage signal. A soft shadow, feather or glow is still non-zero alpha and can legitimately extend the calculated bounds.

On irregular RGB backgrounds, one noisy or graded channel can prevent a tight result. Channel selection is therefore part of the diagnosis rather than a decorative option.

Auto Crop on animated content can produce different bounds from frame to frame. Because Crop changes image resolution/domain, a moving canvas can be undesirable for templates, cache behavior and downstream animation.

For the same reason, X/Y Size should not normally be animated as a zoom control. Blackmagic's Fusion reference explicitly warns that Crop changes image resolution and should not normally be animated.

When the cropped branch feeds Merge.Foreground, the Merge background branch normally remains the format owner. A small foreground Crop therefore does not have to shrink the final composite.

If the cropped branch itself becomes the background/format foundation of a downstream chain, however, its new canvas can determine later working dimensions. Always inspect actual WidthxHeight rather than judging only the visible image.

Crop can reduce the working region before an expensive effect, but this is only safe when pixels beyond the new boundary are not needed by the filter, tracker, optical-flow operation or temporal process.

A practical mental stack is: Size defines the canvas, Offset chooses source placement, constraints link the frame geometry, and Clipping/Auto Crop handle technical boundaries. Avoid fixing one problem simultaneously at multiple levels.

Bundled screenshots anchor current Controls and Auto Crop labels, while the official historical Blackmagic Crop reference provides stable semantics for Size, Offset, DoD and Auto Crop. Internal scripting IDs and conditional controls still require live verification before production automation.