Alpha Controls

The Alpha Cleaner Control filters permit you to make adjustments to the matte to achieve a superior composite.

Alpha Cleaner

A large part of getting a successful key involves having good source footage to begin with. Unfortunately, that doesn’t always happen. Quite often your source image has wrinkles, discoloration, uneven lighting, or other problems, all of which can make for a problem key. Primatte is able to handle a good deal of these problems on its own, but in some cases you will still run into issues. Alpha Cleaner is designed to help in these cases. Simply put, Alpha Cleaner allows you to zap grain or noise, fill in holes in the foreground matte, and fix many other problems that would otherwise require a separate manual matte touch-up in a paint program. Alpha Cleaner works by applying a clean-up pass to your matte, identifying dirt and other artifacts based upon a combination of values, such as their size, alpha level, and proximity to the principle element in your matte.

Cleaning Mode

Cleaning Mode allows you to designate which cleaning operation you wish Alpha Cleaner to perform.

• None leaves the clip unchanged.

• Remove Specks tells Alpha Cleaner to remove specks and noise from the background. (White noise in black areas.)

• Plug Holes removes holes from the foreground object. (Black holes in white areas.)

• Both allows you to both Remove Specks and Plug Holes in one pass. This is a new mode that we are introducing with this release. Users of previous versions of Alpha Cleaner will recall that performing both operations required the user to apply two instances of the filter to the layer. This mode has the same effect as making two passes, but is somewhat more efficient, since some internal buffers can be reused, speeding up the render process.

The next six controls concern the threshold values for controlling the operations of Alpha Cleaner. The controls are Speck Size Threshold, Speck Level Threshold, Speck Connection Threshold, Hole Size Threshold, Hole Alpha Threshold, and Hole Connection Threshold. As you can see, there are three pairs of operations, with each pair concerning either specks or holes. Since the operations are identical except for the type of object they affect, we will discuss the operations below as three pairs, rather than six individual operations.

Size Threshold

The Size Threshold value determines which alpha pixels will be removed based upon their proximity to each noise or chatter area. The slider value controls the size of the clean-up area, with 100% representing the largest area of clean-up (roughly 1/5 of the image size) and 0% representing no clean-up. Increase this value to get rid of larger areas of noise (i.e. larger specks in the black areas or larger holes in the white areas). Noise outside of the threshold range is left unaffected.

Level/Connection Threshold

The Level/Connection Threshold values determine which pixels will be removed based upon the pixel’s luminance value. Noise pixels with a luminance value below the Level/Connection Threshold will be set to 0 (black) or 100 (white), depending on whether you are removing specks or filling holes. The higher the Level/Connection Threshold value, the more pixels will be set to either solid white or solid black.

When you look at your matte, if you have areas of your background or foreground (i.e. pixels which should be 100% black or white) which appear gray, this control will allow you to remove them. However, be advised that if you have any areas of your matte that are supposed to be semi-transparent, such as hair, smoke, or motion- blurred edges, this operation will remove the transparency in these areas. In these type of cases you would be best served by isolating the areas that need to be cleaned with a garbage matte, then using the Alpha Cleaner filter on only those areas.

Note that only pixels within the range of the Size Threshold value will be affected by Level/Connection Threshold.