This example consists of a simple animation where the Photo Lab red channel Gain attribute drives the Radial Ramp tool's Y Center attribute—see Setting Keys Manually, Radial Ramp Tool, and Processing Images with Photo Lab.

To create an animation where the Photo Lab's red channel Gain attribute drives the Radial Ramp's Y Center position attribute:

1. From the Tools tab, drag the Radial Ramp tool from the Image Generation folder to the dependency graph in the Schematic view.
2. Drag the Photo Lab tool from the Color Correction folder to Schematic and place it after the Radial Ramp tool.

   The dependency graph should look like this.

3. 

4. In the Player controls, change the composition's total number of frames to 100.

   

5. In the Radial Ramp tool UI, modify the following attribute values with the following settings:

   Attribute	New Setting
   Start Color Green (G) channel	0.500
   X Radius	30
   Y Radius	16
   X Falloff	85
   Y Falloff	116

   The Radial Ramp should look like this.

   

   You can now set an expression for the Y Center attribute that enables it to be driven by the Photo Lab's Gain, Red channel attribute.

6. Right-click inside the Y Center value field. And select Set Expression.

   

   The Expresso Calculator appears along with a dashed green line at the top of the Y Center value field. This indicates that an expression has been applied.

   

   (a) Bar above value changes to a dashed green line  

7. In the text field at the top of the calculator, type in the following expression string.

   

   This string is typical of what an expression looks like. The Y Center of the Radial Ramp points to the red channel of the gain controls in the Photo Lab tool, and links them. If you are familiar with expressions, you can simply type the expression into the text field (using the correct syntax and order), but if you are not sure of the exact sequence or writing convention, you can cycle through the various expression tokens that make up the string by using Alt + slash (/) on the keyboard.

   NoteBoth Alt keys work, but only the slash (/) that is on the question mark (?) key can be used.

   By opening a Composition Browser view, you can see the socket names of each tool attribute once the menus are expanded. You can use these names as a reference when creating expression strings, as this is how they should look in the expression.

   

   NoteWhen cycling through and selecting a tool's attribute levels, you must separate each level with a period.
8. Open the Photo Lab tool UI.
9. Select Autokey.
10. Change the exposure units to Gain.
11. Mark the red (R) channel of the Gain for keyframing by clicking the R label—see Marking Attributes for Keyframing.

    

12. In intervals of 20 keyframes, increase the gain on the red channel, so that it is at its maximum by frame 100.
13. Play the animation.