Image blur/burn adjustments

So I wanted to implement this effect:


but I only want the first image to appear, so pretty much without it being blurred. I also wanted it to stay a while and then dissolve. How do you do that and how do you control the speed of the animation? Once I turn up the ra, ba … values it does slow down but restarts halfway through the animation. I also need it to stop once it ran the cycle.
It should go from invisible, to visible, then stay and then dissolve.
I’d appreciate any suggestions.