User Manual

Table Of Contents
Alpha Gain slider: Alpha Gain linearly scales the values of the foreground’s Alpha
channel. In Subtractive merges, this controls the density of the composite, similarly to
Blend. In Additive merges, this effectively reduces the amount that the background is
obscured, thus brightening the overall result. In an Additive merge with Alpha Gain set
to 0.0, the foreground pixels are simply added to the background.
Burn In slider: The Burn In control adjusts the amount of Alpha used to darken the
background, without affecting the amount of foreground added in. At 0.0, the merge
behaves like a straight Alpha blend, whereas at 1.0, the foreground is effectively added
onto the background (after Alpha multiplication if in Subtractive mode). This gives the
effect of the foreground image brightening the background image, as with Alpha Gain.
For Additive merges, increasing the Burn In gives an identical result to decreasing
Alpha Gain.
Blend slider: This is a cloned instance of the Blend slider in the Common Controls
tab. Changes made to this control are simultaneously made to the one in the common
controls. The Blend slider mixes the result of the node with its input, blending back
the effect at any value less than 1.0. In this case, it will blend the background with the
merged result.
Additional Controls
The remaining controls let you fine-tune the results of the above settings.
Filter Method: For input images that are being resized, this setting lets you choose the
filter method used to interpolate image pixels when resizing clips. The default setting is
Linear. Different settings work better for different kinds of resizing. Most of these filters
are useful only when making an image larger. When shrinking images, it is common to
use the Linear filter; however, the Catmull-Rom filter will apply some sharpening to the
results and may be useful for preserving detail when scaling down an image.
Nearest Neighbor: This skips or duplicates pixels as needed. This produces the
fastest but crudest results.
Box: This is a simple interpolation resize of the image.
Linear: This uses a simplistic filter, which produces relatively clean and fast results.
Quadratic: This filter produces a nominal result. It offers a good compromise
between speed and quality.
Cubic: This produces better results with continuous-tone images. If the images have
fine detail in them, the results may be blurrier than desired.
Catmull-Rom: This produces good results with continuous-tone images that are
resized down. Produces sharp results with finely detailed images.
Gaussian: This is very similar in speed and quality to Bi-Cubic.
Mitchell: This is similar to Catmull-Rom but produces better results with finely
detailed images. It is slower than Catmull-Rom.
Lanczos: This is very similar to Mitchell and Catmull-Rom but is a little cleaner and
also slower.
Sinc: This is an advanced filter that produces very sharp, detailed results; however, it
may produce visible “ringing” in some situations.
Bessel: This is similar to the Sinc filter but may be slightly faster.
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