Color Controls and Grading Modes

Color correcting clips is possible in the grade control tab of the Audio&Color panel.

Grade controls are separated in grading nodes, a grading node can be understood as one image filter with one or more parameters. A certain set of grading nodes belong to a grading mode. A grading mode is a predefined set of nodes and also helps to work inside certain boundaries concerning the type and order of grading nodes by setting limitations (e.g. CDL and LUT).

Grade Controls

 

figure 1: UI with Grading Controls

UI with Grading Controls

The grade control tab in Silverstack consists of all controls for manipulating the image filtering :

  • Grading mode selector: Switch between the different grading modes available on the drop down menu
  • Grade controls with nodes: Here you find all the nodes for a certain grading mode such as CDL color controls, 3D LUT loading node, saturation etc. Each node can be individually disabled by un-marking the blue check box.
  • Look Source Name: The name of the currently applied look
  • Look actions: The look action menu contains actions …
    • Clear buttons: Clear either all grading nodes (“Neutral”) or just the creative color manipulation nodes (e.g. CDL node) and not LUTs or tone mapping curves (Reset Colors)
      • Using the «Neutral» button you can reset all settings (color and LUT) to a «neutral» state.
      • Using the «Reset Colors» button you can reset the color settings to a “neutral” state.
    • Match Looks
  • Clear buttons: You can clear either the entire look or just the color manipulation (and not LUTs or tone mapping curves)
    • Using the «Neutral» button you can reset all settings (color and LUT) to a «neutral» state.
    • Using the «Reset Colors» button you can reset the color settings to a “neutral” state.

The grade controls consist of the following elements:

  • Grading node: Grouping element containing the actual grade controls
  • Node enabling: Enable or disable the effect of a grading node
  • Edit node structure: Some grading nodes can have variable grading nodes, you can add and reorder grading nodes in the edit mode.
  • Control panels: The control panels button and indicator shows the attached grading panel. You can disable / lock the attached grading panel to prevent unwanted changes.
  • Result curve: The video scopes shows the resulting curves for all enabled grading nodes in the three RGB channels.

 

Grading Modes

Silverstack supports different grading modes designed for specific camera setups and workflow environments.

The node-based design allows you to disable and reorder individual filter nodes to have greater grading freedom. You can disable a certain node by unchecking the blue check box. Have in mind that the processing order is from «top to bottom» when reordering the nodes.

Each grading mode allows different levels of grade customization, as the compatibility of the grades down the workflow creates some restrictions on how the color information has to be processed. For example, the camera compatible grading modes can have the nodes locked in a certain position to ensure the compatibility of the grade.

 

The different grading modes to choose from.

The different grading modes to choose from.

 

The grading modes allowing the greatest level of customization are the Advanced and Freestyle modes.

CDL and LUT

Figure 1: The CDL and LUT grading mode

The CDL and LUT grading mode

The CDL and LUT grading mode offers ASC-CDL controls for the use in a wide range of workflows. For clips recorded in Log color spaces, Silverstack allows to import 3D LUTs or choose from 3D LUT Presets.

In order to support workflows that apply CDL in log gamma as well as in video gamma, the order of LUT and CDL filters can be changed when using the CDL Advanced grading mode. The CDL and LUT mode can also be used with Rec.709 clips without adding a 3D LUT.

The color controls for the CDL and LUT grading mode consist of:

  • ASC-CDL controls node:
    • RGB Shadows, Mid-tones and Highlights color wheels

      figure 5:

      ASC-CDL color wheels

 

  • Saturation slider node

    figure : Saturation node

    Saturation node

 

  • Import of 3D LUT node: The CDL and LUT grading mode can import 3D LUTs and CDL files and can export ASC-CDL files.
    • 3D LUT Import options with averaged curve displays for each channel

      figure 4: 3D LUT node

      3D LUT node

 

CDL Advanced

Allows you to add and reorder multiple nodes on advanced workflows.

Alexa Looks (Deprecated)

This mode is designed to create .xml ALEXA Looks compatible with ARRI ALEXA cameras. More information in the article Using the ALEXA Looks grading mode.

Freestyle

This grading mode has been created to allow complete grading freedom. For this reason, there are some limitations on the available export formats for looks created on this mode.

ACES CDL

A mode adapted to the ACES standard. More information in the article Using the ACES grading mode.

ACES CDL Advanced

A mode adapted to the ACES standard. Allows you to add and reorder multiple nodes on advanced workflows.

ACES Freestyle

This grading mode has been created to allow complete grading freedom inside an ACES pipeline.

Varicam Compatible

This mode is designed to create 3D LUTs and looks compatible with Panasonic Varicam 35 cameras.

Amira Compatible

This mode is designed to create .aml AMIRA Looks compatible with ARRI AMIRA cameras.

ARRI CAP Compatible

This mode is designed to create .aml Looks compatible with ARRI CAP (Camera Access Protocol).

 

Grading Nodes

CDL Node

The CDL node contains a color wheel for Offset, Power and Slope. It can be used to adjust the color on the image.

CDL grading node

ASC-CDL files can be directly loaded and saved to/from the CDL node (supported format: *.cdl).  Click the gear button on the left side of the CDL node and select if you want to load or save a CDL.

Please be aware that the ASC-CDL specification always includes a saturation value. When one saturation node is present CDLs will be loaded and saved from/to the present saturation node. When multiple CDL and saturation nodes are present you will be pointed choose the saturation node you want to load the saturation to (indicators A,B,C etc.).

 

The CDL node has several interaction types with different controls for different interaction styles. The interaction types of one CDL node all work on the same set of CDL values, so changing controls in one interaction type might change control positions also in the other interaction types.

The available interaction types:

CDL interaction type:

CDL node – CDL interaction type

The CDL interaction type allows to manipulate the nine values of the SOP triples (for each color channel R, G, B) of the CDL. The values in the nine text fields are the same values as in an exported ASC-CDL file.

The color wheels have a global control (in the bottom left of each wheel), an indicator around the ring shows if the global control is modified. Changing the wheel control doesn’t change the gloabl luma of that control, e.g. the channels are balanced and the global control doesn’t change by changing the wheel position.

Lift, Gamma, Gain (LGG) interaction type:

CDL node – LGG interaction type

The LGG interaction type allows to manipulate lift, gamma, and gain (LGG) values as known from other grading systems. These control values are mapped to CDL values in the background. The nine text fields show lift, gamma, and gain values (not ASC-CDL values) – switch back to the CDL interaction type to see the CDL values of a certain setting of LGG values.

Note: Although ASC-CDL doesn’t specify limits of its values, some 3rd party software products limit values in their ASC-CDL grade controls. An indicator (“i”) on the very right of the grade UI Silverstack indicates that values are out of the range that is commonly accepted.

The color wheels have a global control (in the bottom left of each wheel), an indicator around the ring shows if the global control is modified. Changing the wheel control doesn’t change the global luma of that control, e.g. the channels are balanced and the global control doesn’t change by changing the wheel position.

Simplified (SPL) interaction type:

CDL node – SPL interaction type

The SPL interaction type allows to manipulate the values of the CDL filter with the controls Contrast, Stretch, Warmer and Greener.

Increasing the contrast control makes the resulting curve steeper by clipping black and white. Increasing the stretch control increases contrast in the highlights, while decreasing stretch increases contrast in the shadows. Increasing the warmer control gives the image a warmer appearance by giving the shadows a warmer tint while the whites stay unmodified. Increasing the greener control gives the image a greener appearance by giving the shadows a greener tint while the whites stay unmodified.

Printer Lights (PRT) interaction type:

CDL node – PRT interaction type

The PRT interaction type allows to simulate a color correction based on printer lights. Printer lights can be approximated by an offset in camera log encodings. Additional buttons for each color channel allow for changes in fixed steps.

ASC-CDL files can be directly loaded and saved to/from the CDL node (supported format: *.cdl).  Click the gear button on the left side of the CDL node and select if you want to load or save a CDL.

Please be aware that the ASC-CDL specification always includes a saturation value. When one saturation node is present CDLs will be loaded and saved from/to the present saturation node. When multiple CDL and saturation nodes are present you will be pointed choose the saturation node you want to load the saturation to (indicators A,B,C etc.).

The size of the color wheels can be adjusted in the Preferences menu. Just choose a size that fits your display resolution.

The CDL node can be controlled by an external hardware grading panel. To have more information on how to use it, please check the following articles:

Saturation Node

Just drag the slider to either side to increase or decrease the saturation on your look.

figure : Saturation node

Saturation node

3D LUT Node

The 3D LUT node is designed to load your own 3D LUTs by pressing the «Load…» button. Alternatively, you can also use one of the available preset 3D LUTs to convert the image to a Rec.709 color space.

figure 4: 3D LUT node

3D LUT node

Supported formats for loading into the 3D LUT node are:

  • Adobe Speedgrade (.cube; size 32,33, 65)

  • Assimilate Scratch (.3dl; size 32)

  • Panasonic Varicam (.vlt)

  • Autodesk Lustre ( .lut) 

  • Truelight (.cub)

1D LUT Node

The 1D LUT lets you load your own 1D LUT file. Click the “Load…” button and select the 1D LUT you want to load to the node.

figure:

1D LUT Node

In contrast to the curve node the LUT in the 1D LUT node can not be edited afterwards.

Supported formats are:

  • *.txt
    • channels: 3
    • range: 0.0 … 1023.0 (float)
    • header: “R G B – HDLINK GAMMA TABLE”
    • entries: 1024
    • row example: “221.37 221.37 221.37”
  • *.data
    • channels: 4
    • range: 0 … 16383 (integer)
    • entries: 16384
    • row example: 15040,15040,15040,15040
  • *.lut
    • channels: 3 (4 columns with leading index (0…65535, R, G, B)
    • range: 0 … 65535 (integer)
    • header: “LUT16”
    • entries: 65536
    • row example: 45490 58366 58366 58366

RGB Curves Node

 

figure : Curve node

RGB Curves node

The RGB Curves node lets you apply precise curve adjustments to master RGB values or to individual luma, red, green, blue and/or custom color channels. Click on “Edit” to open the RGB Curves Editor window, which allows you to precisely grade your footage:

  • There are two modes to choose from:
      • “RGB-Based” adjusts the selected color channel including its luma and saturation values, while the “Master” curve is a ganged RGB curve influencing the red, green and blue channel at the same time
      • “Luma-Based” adjusts the colors red, green, blue and/or the custom set color without influencing their luma and saturation values, while the “Luma” curve can be adjusted independently
  • In the “Custom” color curve you can pick a custom target hue, for adjusting a certain color in your image precisely
  • To add a curve point just click on a curve, and in order to modify it’s value just drag and drop. You can adjust curve points using the left/right and up/down arrow keys as well.
  • To remove a point, select the point and press Backspace.
  • When you move your mouse over the curve editor, the graph shows you the value of the exact point where it is. When the mouse pointer is not moving or it is outside of the curve editor window the values of the currently selected curve point are being displayed.

RGB Curves editor window

More information on how to use the editor can be found in the article Using the RGB Curves Editor.

HHS Node

The HHS node –Hue to Hue and Saturation– is a new kind of node that allows you to map a certain hue on the image and replace it by another color with different hue and saturation. Here is an example where the red has been desaturated, but the other colors remain the same:

 

HHS comparison

 

The HHS editor allows you to drag and drop the hue circles to another location on the color space to replace the original color with another one.

 

figure 5: HHS editor

HHS editor

Amount Slider

CDL nodes, RGB curve nodes, HSL curve nodes and HHS nodes have an amount slider which allows to fine-tune the effect of the associated grading node. There is an intensity level indicator on the right hand side of the node. When clicking on it, you can adjust the intensity in a popover window, either with a slider or by typing in a value from 0-100%.

Note: The initially set values in CDL nodes remain the same when changing the intensity. When you create a shot, the values of the grade are re-calculated with the applied intensity amount and saved as new resulting values in the shot table.

CDL node with amount slider

Grading Panel Support

Silverstack supports the use of hardware grading panels for the grading functionalities. The following panels are supported:

  • Tangent Element Tk
  • Tangent Ripple
  • Tangent Wave
  • Tangent Wave2

Connect the hardware panels to Silverstack to precisely and physically manipulate your grades.