ACP

Advanced primary & secondary colour processor

ACP is Digital Vision’s third generation colour corrector designed primarily for advanced tape-to-tape colour
correction. For the demanding jobs, additional primary colour corrector layers with Viper keying provide a power boost. For creative effects, additional features such as adjustable transfer functions (curves) and dedicated vignette layer are included.

Before ACP	After ACP

The ACP, together with the closely integrated Valhall control system, has been developed together with some of the most experienced colourists in the business.

Key features

• 4:4:4:4 YRGB or 4:4:4 RGB path primary colour corrector with adjustable transfer functions and Custom Curves
• 1 Primary base layer plus additional 2 primary colour corrector layers with advanced Viper keying
• 4:4:4 YCbCr 6 channel secondary colour corrector with advanced HSL colour isolation, adjustable
  despeckle filter, blur filter and key areas
• Dedicated vignette layer including vignette key area with adjustable roundness
• Output RGB Legalizer with final Hue, Sat and Lum adjustments
• Available in SD and HD RGB formats

Primary colour processor

The internal signal processing of the primary colour corrector is structured around four channels, one
luminance path and three chrominance paths, each one processed with the same bandwidth. The primary
can be configured for use of all 4 paths (Y+RGB) or 3 paths (RGB). The use of Y+RGB paths allow luminance
gain and black changes to be made without affecting or needing to realign colour balance. Inversely, when
grading colour, the luminance level remains constant.

Further, the internal processing has been designed so that no truncation errors are introduced in the processing chain. This is especially important for certain parameters like gamma correction in order to avoid any stepwise action of the curve.

The ACP also features user definable transfer functions and thresholds for black, gamma and gain control, which are useful when perfect match in the primary colour correction stage is required. For even greater flexibility, precise control and creative effects, separate Custom Curves for YRGB are available. In addition to the base layer, two extra layers of primary colour correction including Viper keying are available. Each of these layers can process the output of the previous layer, the output of the base layer or the original
picture.

Advanced Viper keying

The advanced Viper keying, is used to isolate areas in the picture for the two additional primary colour corrector layers. The user interface has been designed to provide both speed of operation as well as a high level of control over the key area. This has been accomplished by assigning controls on the Valhall Colour Corrector panel for parameters such as position and shape and at the same time providing accurate control with the mouse pointer.

All area shape adjustment uses the video monitor as the primary display for the key area. The Viper keying
provides the colourist with the choice of one out of two key shapes: rectangle or ellipse that can be positioned, resized and rotated.Adjustable soft edge, with the choice of different profiles, is also provided.

Secondary colour processor

The secondary colour corrector offers six functionally parallel channels with independent discrimination
and processing in the hue, saturation and luminance domains. The HSL analyzer features adjustable
soft edges and also a noise filter, providing cleaner processing. The channels can be overlapped thus adding their respective adjustment to the final result.

Together with the Valhall Control System, the ACP offers the Eyedropper - which enables the user to point
at a desired colour to be manipulated whereby the discrimination centre point is automatically identified and
set. The size of the sample area of the eye-dropper can be set.

A mask, out of 6 available, can be enabled providing an overlay showing which parts of the picture will be
affected by the selected vector(s). Rectangular key areas (1 per each vector) can be used to further isolate the affected areas in the picture. Both the hit from the HSL analyzer and the key area can be inverted separately for each vector.

Vignette layer

The vignette layer is typically used to mimic the shadow effect of lenses or to frame pictures with a selectable
colour. The vignette layer includes a dedicated rectangular key area, similar to the Viper key area, but with adjustable roundness. They key area can be positioned, resized and rotated. Adjustable soft edge, with the choice of different profiles, can be applied.

Output processing

After Primary and Secondary colour processing, a final output processing stage is available including an RGB
legalizer with adjustable levels as well as hue, saturation and luminance controls.

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