I've noticed that when using a .png image with text-only as a layer in a slideshow, the image jerks into place using fade as opposed to a smooth transition. If there is a background image behind the text, the transition is smooth. Also, text on a transparent background when switching overlays is smooth.

Why can't the overlay animation and the slideshow animation be the same? Why are they different?

This often limits what I want to do with slideshows.