Every compositor will have to transform a multitude of images and visual elements to make a shot stand out and while there are a lot of ways to complete this task there is one very important thing you must understand to maintain the highest quality.
Today we’ll be learning about “concatenation”, what it is and how it is calculated inside of Nuke. We will start with the definition of the word.
a series of interconnected things or events.
"a singular concatenation of events unlikely to recur”
the action of linking things together in a series.
Inside of Nuke, certain nodes will concatenate. Crop, Transform, Reformat, Corner Pin, iDistort, and Mirror to name a few. Here I have an image of the famous Mario I got off of Google Images. I’ve reformatted it to HD 1080 for this example.
Here I placed two Transforms, one set at a scale of “0.5” and the second one at a scale value of “2”. When viewing the last node and selecting both transforms and disabling them on and off we can see the image is not changing. It’s a perfect scale treatment, being scaled down and back up without any issues or degradation of quality.
Now let’s put a Grade node between these two Transforms. You’ll immediately see that we have completely destroyed the quality in the image between the two scale calculations. This is because we have broken the concatenation between the two Transforms and Nuke is forced to recalculate the change in scale by using the currently selected filter, in this case “Cubic”. Changing the filter will result in different outputs but it will never be the same as the original. The quality is lost.
Here you can see the left side has the grade between the two transforms, and on the right side the grade is after the two transforms.
By keeping your transforms (and all other image transformation nodes) together, they can all concatenate and you will preserve the images intended quality. Once you have finished transforming the image you can then apply any other nodes after.
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