Defect Manager

Defect Manager  |  Dirt/Dust  |  Scratches

Defect Manager

The defect manager controls are used to specify how dirt, dust and scratches are detected at each frame. Each set of controls can be switch on or off by clicking the appropriate On or Off button.

Defect Map

When enabled, dirt, dust and scratches will be cleaned according to the defect map stored in the image alpha channel. Typically, defects will be identified as either Bright or Dark pixels.

By default, this control is set according to the Defect Map setting in the current project. The contents of the clip's alpha channel can be displayed using the RGBA controls in the Cinema window or using the appropriate keyboard shortcut (the A key by default).

Note: It is recommended to examine the contents of the clip's alpha channel before adjusting these parameters, to ensure that pixels containing defects are correctly identified.

For clips containing a graduated defect map, the Alpha % slider can be used to specify the threshold at which a defect is detected. For example, setting the defect map to Bright, and the Alpha % to 90 indicates that all pixels with an alpha value larger than this value will be considered defects. Setting the defect map to Dark and the Alpha % to 10 indicates that all pixels with a alpha value below 10% will be classed as defects.

The Dilate parameter can be adjusted to apply a dilation operation to the detected defects if required, increasing their size by the specified number of pixels.

Pixels that have been identified as defects using these parameters can be displayed in the Cinema window by enabling the Show Defects option beneath the holdout mask controls. This will display an overlay where light blue pixels indicate defects.

Dirt/Dust

When not using a defect map, dirt and dust marks scattered over the image area can be detected automatically, provided they exist for only one frame at a time. Dirt can be detected as either Bright or Dark pixels in the image. Both bright and dark dirt marks can also be detected at the same time if required by selecting Both.

The threshold for dirt/dust detection is controlled using the Detect % parameter. This specifies the minimum change in pixel intensity from frame-to-frame for a pixel to classified as a defect, so reducing this parameter will detect fainter dirt or dust marks (the default value is 10%).

Whilst reducing the Detect % parameter to a small value may detect very feint dirt or dust marks, it may also cause more areas of the image to be incorrectly classified as containing defects. Typically this can occur in parts of the image containing significant motion that cannot be compensated for automatically. The Reject % parameter can be used to remove these incorrectly classified areas. The default value for this parameter is 50%, and increasing it will remove more dirt/dust areas from the image, where low confidence areas are removed before higher confidence areas.

Pixels that have been identified as dirt/dust using these parameters can be displayed in the Cinema window by enabling the Show Defects option beneath the holdout mask controls. This will display an overlay where red pixels indicate those containing dirt or dust.

The amount by which pixel colours have changed when compared to the original can be examined by enabling the Show Difference option beneath the holdout mask controls. Neutral grey value indicates no difference, and brighter/darker pixels indicate significant changes in pixel colour.

Scratches

When not using a defect map, scratches can be detected automatically using these controls. Scratches can be detected as either Bright or Dark pixels in the image.

The threshold for scratch detection is controlled using the Detect % parameter. This specifies the minimum intensity difference between a scratch and the surrounding image pixels, so reducing it from the default value of 10% will cause fainter scratches to be detected. The Width parameter specifies the maximum width of a scratch in pixels, and the Length % parameter specifies the minimum vertical length of a scratch as a percentage of image height. The default scratch width is 4 pixels, and the default length is 10%.

The Dilate parameter can be adjusted to increase the width of each detected scratch before it is fixed, which can sometimes provide a more visually pleasant result.

Pixels that have been identified as scratches using these parameters can be displayed in the Cinema window by enabling the Show Defects option beneath the holdout mask controls. This will display an overlay where green pixels indicate those containing scratches (Note, if a pixel has been identified as a scratch or dirt/dust, it will be coloured yellow).

The amount by which pixel colours have changed when compared to the original can be examined by enabling the Show Difference option beneath the holdout mask controls. Neutral grey value indicates no difference, and brighter/darker pixels indicate significant changes in pixel colour.