Movies of fish swimming underwater typically work really well as source video for temporal image processing effects. In this post we’ll explore the use of the Temporal Difference Matte effect, and also discuss how to auto-correct the white balance of images or video taken underwater.
The paint action sequence (PASeq) below was used to generate the effected image shown above.
The first action step is based on the Temporal Difference Matte, which is one of the temporal image processing effects. It works by processing multiple frames of a source movie to create a single output image. The effect tries to analyze frame differences in a movie (computed as a difference from a variable standardized background), and then mattes the various difference images together to create an effect that can accent moving objects or details across the multiple frame movie input.
Temporal image processing effects are designed to process source movies, so they won’t do anything if you just have a static image loaded into the source are. Your loaded source needs to be a movie file. For this particular temporal image processing effect, a static non moving camera positioning usually works best.
The 2nd gallery image above shows the Editor settings for the Temporal Difference Matte effect, as well as the Source Area. Note that a 144 frame source movie of fish swimming underwater is loaded as the the current source. The source movie transport shows that the loaded source movie is currently set to frame 1 of the 144 frame movie file.
The Base parameter determines how the standardized background that will be used to compute frame differences for matting is computed. The Backing parameter determines how the initial backing image for the effect is computed. The Matte parameter determines how the multiple frame differences generated internally by the effect (between an input frame and the standardized background) are matted into the Backing image. By playing with the different options for these 3 parameters you can create a variety of different kinds of visual effects.
Most temporal image processing effects have standard Size, Frame Inc (increment), and Symmetry parameters. These 3 parameters are used to specify the movie frame input time window for the temporal effect. Size sets the number of input frames that will be used to compute the effect. Frame Inc determines the spacing between adjacent input frames to the effect. Symmetry determines how the input time window is positioned relative to the current source movie frame position.
Since the source movie is positioned at frame 1, we needed to set the Symmetry to Forward. I wanted to position the input window across most of the entire source movie. So I set the Size to process 13 input frames,and set the Frame Inc to 10 so the input window spanned a 130 frame time window, starting at the first frame in the source movie. Size times Frame Inc equals the overall size of the input time window.
Automatic White Balance Adjustment
Video taken underwater typically has a blueish coloring to it associated with the effect of light passing through water. Sometimes you might like the artificial tinted coloring associated with this visual look, but other times you might want to remove it to get a better sense of the true coloring of the objects in the image. The blueish tinted coloring can also give an underwater image a somewhat washed out looking appearance.
Studio Artist has a special image processing effect called White Balance that can be used to auto-correct the white balance of an image or video frame. If you look at the PASeq we used to generate our effected image above, you can see that we used the White Balance ip op as the second action step in the PASeq. The White Balance ip op automatically adjusts the white balance of it’s input to try and remove any global color tint (in this case the blueish coloring tint offset associated with underwater photography).
The gallery below shows the White Balance control panel settings I used for the PASeq processing shown above.
The 2nd and 3rd gallery images above show a before and after underwater image frame, where the after image is processed by the White Balance ip op with the effect settings shown in the 1st gallery image to auto-correct the white balance of the before image. Note how the blueish coloring of the before image is removed in the after image, and the overall image contrast is also improved in the after image.
The final action step in the PASeq above used the Image Compressor ip op to add some additional adaptive contrast boost to the final effect output. The Image Compressor control panel settings used in the PASeq are shown in the 4th gallery image above.
