Okay, so I just found some performance issue when changing the FOV.
I am using an FInterp to go from something like FOV10 to FOV90 (sniper scope) in a matter of half a second. There is quite hefty FPS drop. Goes from about 90 (zoomed in) to under 10 (during zoom-out) to about 60-70 (zoomed out).
Hi order66,
I just tested this in 4.8 Preview 4 but I couldn’t get your results. My FPS would stay around 60-70 at all times. Could you provide a screenshot showing how you are setting up the FOV change?
Also your Dxdiag (system specs) could be helpful as well.
Hi order66,
We haven’t heard back from you in a few days, so we are marking this post as resolved for tracking purposes. If you’re still experiencing this issue, please feel free to post back here with additional information.
Cheers,
TJ
Same problem here.
I change the FOV with a scope and when it zoom to normal I get a heavy FPS drop.
I think it’s a LOD problem.
Cause I can see the reloading of all textures after zoom out from low to the best LODs.
June of 2016 and the issue is still not fixed!
With this heavy problem I cannot use a sniper scope! 
Hi Daniel,
I’m going to need some additional info:
Post your Dxdiag (system specs)
How many actors do you have in your environment?
I tested this in the default 1st Person Template but couldn’t get your results unless I did an extreme test. With about 200-300 active physics objects, I do get about a 15-20 FPS drop on FOV change. However, this is expected behavior considering the amount of physics objects and then rapidly changing the FOV on top of that.
Changing from a very small FOV (like 10) to a normal FOV (90) also makes the performance worse.
Try testing this with a lot of trees (which go from actual meshes (with FOV10) to sprites (FOV90) ) - which isn’t such uncommon example.
Hi order66,
This is expected behavior when dealing with lots of meshes, LOD levels, and large FOV changes… What needs to be done in your project now is optimization.
Take a look at the Profiler Tool and gather data. Then investigate best practices on how to optimize what you can. You should also look into how many Draw Calls are being made and try to combine as many as possible.