Blackmagic Design Ultimatte 12 Manual De Operaciones página 42

4 Click 'sample wall'. Notice that 'floor cursor position' is now enabled and the floor
cursor position is automatically available for you to adjust. Make your desired changes
to the second cursor position. For best results, select an area on the floor where
you see lighting glare or veiling, and avoid shadow areas that you want to retain in
the matte.
5 Click on 'sample floor'. Your selection will save these screen values as your new
reference and the view will switch back to the monitor out setting you were last using.
Filter
The filter settings let you remove ringing artifacts that may appear in the transition edges,
plus provides noise reduction and noise generation settings to help blend foreground and
background elements together.
4:2:2 Correction level
In a Y,Cb,Cr 4:2:2 video image, objects with high contrast and sharp transitions can exhibit
a small edge artifact when used for green screen compositing. This is due to the reduced
bandwidth of the Cb and Cr color difference channels.
For example, a dark colored foreground object with sharp transitions shot against a bright
green screen will show an overshoot and an undershoot at the transitions. This is known as
ringing. These ringing artifacts are shades of black and white and will be treated as foreground
objects when processed, similar to gray strands of hair. When the green screen color is
removed and replaced by a dark background, a dark foreground object will show bright gray
edges at the transitions.
The 4:2:2 correction feature eliminates or reduces the ringing artifacts. No foreground object
detail is lost in this process.
4:2:2 correction is set to 100% by default. To make an adjustment, decrease the setting while
monitoring the program output until you notice the ringing artifact appear in the composite,
then gradually increase until it is no longer visible.
Noise Reduction/Generation
All video recorded using a video camera will contain a minor level of noise in the image.
When composited with pristine, noise free graphics generated by a computer, the difference
between sources can be noticeable.
To help blend elements, Ultimatte has noise reduction and noise generation settings that let
you clean noise from the foreground, and add noise to the clean areas of your composite.
For example, noise can be generated in the background or layer source, or areas of the
foreground that have been masked by a garbage matte.
There are two types of noise reduction. Median, and average.
To reduce noise:
1 Toggle between the average and median noise reduction types by clicking the
selection button on the left side of the functions section.
2 Now click the corresponding setting next to the selection button to set a noise
reduction level. Click multiple times to gradually increase the level. There are four
levels of noise reduction to choose from.
Advanced Ultimatte Controls 42