... There are number of features that can be set by the user in the Sparkle Dialog box. ... The Sparkle plug-in computes the luminosity (level of whiteness) of each pixel in the image (the user can see this when the progress window labeled Generating luminosity array... is displayed). ... The threshold value is currently a slider/text field pair which have a precision of .0001. ... Like the Threshold value, the Flare Intensity has both a slider and a text input field for specifying its value. ...