Why does camera FOV effect Ray Traced Distance Field shadows performance?

I setup Ray Traced Distance Field shadows in my level and they seem to perform pretty well, except when I trigger my weapon zoom and adjust the camera FOV; performance tanks and I lose about half my frames.

Any ideas what’s going on here? Are there ways to avoid that?

if the field of view was increasing i’d say that it’s because you’re rendering more but it sounds like you’re shrinking the FoV. if the distance field is dynamic it may have to suddenly recompute a bunch of stuff.

Yeah…def shrinking the FOV here on zoom. Also, i might understand a short hiccup for recomputing, but when framerate tanks, it stays tanked for as long as you having the weapon zoomed.