I have set some low default values for my camera brightness because my game is really dark. However when I want to modify them in the character blueprint there are no visual changes, please help!
I copied your setup and everything seems to work as expected for me in 4.9.
Can you confirm that the set post process settings node is being called?
Is it possible that a post process volume is overriding the camera settings?
Thank you for your reply! Sadly I don’t believe neither of those two things are causing the problem since I dont have any post process volumes in my level aside from the camera settings and I tried implementing the code shown in the attached image to make sure the node is called. The only changes I believe that I have made concering camera brightness should be the camera defaults.
This annoys me, but the solution is probably really simple, haha! 
Just tried a quick experiment… Opened up the Third person template and first removed the standard post process volume. After that I changed the default camera brightness as shown in the attached image. Then I implemented the “Set post process setting node” with almost identical input as the default values. However when F is pressed then the brightness goes back to normal as shown in the attached image. Why? Am I missing something?
Those are the same results that I saw as well. I’m thinking maybe your issue has to do with how the lighting in your level is set up?
I just tested this in a completely empty map with a single dim point light. Using the settings above, the change in exposure from 0.03, 0.05 to 9, 10 is unnoticeable. Starting the camera with values 0.003, 0.005 and then setting them to 9, 10 is a visible change however, so updating the settings does seem to work.
I guess you just need to play around with the lighting in your map?
P.S. using atmospheric fog plus a sky light seems to have a huge influence on camera exposure.
I’m also testing in an empty level right now with a single light attached to the character, but no progress.
It just doesn’t make any sense to me that the “Set post process setting” node has such minimal effect since having 9 and 10 as max/min camera default values gives the effect I desire. But I only want it for a short period of time, hence the desire to change it dynamically in my blueprint.
I do appreciate the help, thank you very much! I guess I have to fiddle around a bit more to find something that looks somewhat acceptable.
The values that you have entered are only used if “automatic exposure correction” is turned on in the Project Settings → Renderer section. Otherwise, you need to use “Exposure Bias”.