An effect simulates a photographic filter. To apply an effect to the current image, click the effect's icon on the Effects tab. Effects are applied to entire images.
Each effect icon shows an approximation of the effect it will produce when applied to the current image. The top five icons each have a tiny 1 in the lower-right corner, denoting that their effect is applied instantly; all other effects require you to select options or adjust settings. To remove the most recently applied effect, click the Undo button. To reapply a removed effect, click Redo.