frameBlendMerge v1.4

THE PROBLEM

This tool came about as an alternative way of generating a cleanplate. I was working with footage that had a lot of falling snow, and needed to remove it to leave just the background.

My Auto Cleanplate tool would not work as the snow particles were too small to track with optical flow. Doing any time-based blending of frames would not work, as FrameBlend would leave bright streaks through the shot.

I figured that because everything that I wanted to remove was brighter than the background, I could merge a number of frames using a 'min' operation. The FrameBlend does not allow for different operations other than averaging between all input frames. I needed a way to automatically blend a large number of frames, but using an operation other than just 'over' - a way of combining a FrameBlend with a Merge.

THE SOLUTION

The solution is pretty crude, but does the trick. I created a gizmo that takes a frame range and an operation as it's input.

When you hit the 'update' button, a script loops through and creates a FrameHold for every frame in the range. These are then all attached as inputs to a single Merge node, which has our selected operation set as its blending mode.

I applied this to my falling snow footage and created a cleanplate by blending 20 frames.

ADDITIONAL CONSIDERATIONS

Using a 'min' operation works great for removing bright parts of the image from a dark background (fire, sparks etc.), but with a 'max' operation could just as easily remove dark objects (birds flying against a bright sky etc.). I have included all of the available operations available in a Merge node, as there may be many scenarios where different operations will work better for a specific task. Since creating this tool I came across FrameMedian by Mads Hagbarth. This uses mathematical averaging over a frame range to achieve a similar result. His tool is very well made and will, in many cases, create a better result.