Sometimes we want to show two (full-screen) images at the same time by blending them together. With analogue slides we had the additive blending on the screen. In PTE we can put image 1 on top of image 2, and we can set the opacity of image 1 to 50% (alpha-blending). This is indeed an addition, but only with half the colour values. This is the reason why the results of this kind of blending often show a lack of contrast.
Since version 11 PTE we can use the feature of "Nested Color Filters", the value of which I noticed only recently. In the situation above, it allows us to overcome the restictions of alpha-blending, and we can create additive blends in which the images have higher proportions than just 50%. An application is shown in the attached project:
KerzePlusLaterne.zip
A bit more sophisticated methods have been applied to create the following video (texts in German):