Logical operations are applied separately to each of the red, green, and blue components of images. You can apply Logic Ops
commands to combine the RGB channels of corresponding pixels from two source images, described as follows.
- Add
-
Adds the luma values of the corresponding pixels from two source clips and assigns the resulting value to the corresponding
pixel in the generated clip. If the result is greater than 255, the pixel in the destination clip is clamped at a value of
255 (white).
The order in which the two source clips are selected does not affect the result of the Add operation. The generated clip is
brighter than either of the two selected source clips.
- And
-
Applies a bitwise logical AND operation between the RGB channels of corresponding pixels in the two source clips. The order
in which the two source clips are selected does not affect the result of the AND operation.
- AndInv
-
Applies a bitwise logical AND operation between the negative of the RGB channels of the pixels of the front clip and the RGB
channels of the pixels of the back clip.
- AndRev
-
Applies a bitwise logical AND operation between the negative of the RGB channels of the pixels of the back clip and the RGB
channels of the pixels of the front clip. AndRev and AndInv yield the same result if you switch the order of the two source
clips.
- Difference
-
Calculates the difference between the RGB channels of the corresponding pixels of the two source clips. As opposed to Subtract,
the order of the two source clips does not matter, as the smaller channel value is always subtracted from the larger channel
value.
Blending with white inverts the colour channel values; blending with black produces no change.
- Exclusion
-
Adds the RGB channel values of the corresponding pixels from the two source clips, then subtracts twice the product of these
channels. The order of the source clips does not matter.
- HardLight
-
Multiplies or screens the selected colour of the front clip onto the back clip, depending on the blend colour. The effect
is similar to shining a harsh spotlight on the image, and greatly reduces the contrast levels in the image.
If the blend colour (light source) is lighter than 50% grey, the image is lightened as if it were screened—this is useful
for adding highlights to an image. If the blend colour is darker than 50% grey, the image is darkened, as if it were multiplied—this
is useful for adding shadows.
- Max/Lighten
-
Compares the RGB channels of each pixel of the source clips individually and returns the larger of the two values. The order
in which you select the source clips does not affect the result.
- Min/Darken
-
Compares the RGB channels of each pixel of the source clips individually and returns the smaller of the two values in the
resulting clip. The order in which you select the source clips does not affect the result.
- Multiply
-
Multiplies the RGB channel values of corresponding pixels of the two source clips and normalizes the result by dividing by
255. The resulting RGB channel values are assigned to the corresponding pixels in the generated clip.
The order in which you select the source clips does not affect the result.
- Nand
-
Applies a bitwise logical AND operation between the RGB channel values of the corresponding pixels of the two source clips,
negates the result, and assigns the result to the channels of the corresponding pixels in the generated clip.
- Nor
-
Applies a bitwise logical OR operation between the RGB channel values of the corresponding pixels of the two source clips,
negates the result, and assigns the result to the channels of the corresponding pixels in the generated clip.
The order in which you select the source clips does not affect the result.
- Or
-
Applies a bitwise logical OR operation between the RGB channel values of the corresponding pixels of the two source clips,
and assigns the result to the channels of the corresponding pixel in the generated clip.
The order in which you select the source clips does not affect the result.
- OrInv
-
Applies a bitwise logical OR operation between the negative of the RGB channel values of the pixels in the front clip and
the RGB channel values of the corresponding pixels in the back clip, and assigns the result to the channels of the corresponding
pixels in the generated clip.
- OrRev
-
Applies a bitwise logical OR operation between the RGB channel values of the pixels in the front clip and the negative of
the RGB channel values of the corresponding pixel in the back clip, and assigns the result to the channels of the corresponding
pixels in the generated clip.
OrRev and OrInv yield the same result if you switch the order of the two source clips.
- Overlay
-
Multiplies or screens the colours, depending on the RGB channel values of the first clip you select. Patterns or colours overlay
the existing RGB channel values while preserving the highlights and shadows of the first clip's colour. The first clip's colour
is not replaced but is mixed with the second clip's colour to reflect the lightness or darkness of the original colour.
- Screen
-
Multiplies the inverse of the second clip's colours with the colours of the first clip. The resulting colour is always lighter.
The colour remains unchanged when you screen with black. Screening with white produces white. The effect is similar to projecting
multiple photographic slides on top of each other.
- SoftLight
-
Shines a soft, diffuse light on the image. If the blend colour (light source) is lighter than 50% grey, the image is lightened.
If the blend colour is darker than 50% grey, the image is darkened.
Using this mode with a black frame results in a very dark effect, with white a very bright one.
- Subtract
-
Subtracts the RGB channel values of the pixels from the back clip from the RGB channel values of the pixels from the front
clip and assigns the result to the RGB channel values of the pixel in the generated clip. If an RGB channel value from the
back clip is larger than the corresponding channel value in the front clip, yielding a negative result, that result is clamped
at 0 (black).
The order of the source clips is important since the back clip is subtracted from the front clip. The resulting clip is always
darker than either of the two source clips.
- Xnor
-
Applies a bitwise logical exclusive OR operation between the RGB channel values of the corresponding pixels of the two source
clips, negates the result, and assigns the result to the channels of the corresponding pixels in the generated clip.
The order in which you select the source clips does not affect the result.
- Xor
-
Applies a bitwise logical exclusive OR operation between the RGB channel values of the corresponding pixels of the two source
clips, and assigns the result to the channels of the corresponding pixels in the generated clip.
The order in which you select the source clips does not affect the result.
To use logical operations:
- In the Processing menu, click Logic Ops.
The Logoc Ops controls appear.
- Select the blend mode you want to use from the Logical Operations box.
- Select an option from the Input Mode box. You can select either a Front and a Back clip, or a Front, Back, and Matte clip.
- Specify the transparency value.
Use the default value of 0.0% to combine your clips completely. Using any value above zero results in an effect in which the
specified layers are combined, but you can see though the combined clips to the original Back clip.
- Select a rendering option from the Clamp Render box. This box provides options for colour and luminance values on output in
the 16-bit floating point processing pipeline.
- Select the source clips to be used for the operation. The order in which clips are selected affects the outcome of some operations.
NoteIf you want to use clips of different resolutions, resize them according to the common destination resolution. See
Resize.
- Select the destination reel.
The generated clip appears on the destination reel.