Whenever I use the emissive effect it will cause the whole scene to glow instead of just the thing that should glow. For example lets say you have a lightsaber since thats something we're all familiar with. You want the blade portion to glow, but not the hilt or the person holding it. The only thing I've discovers thus far…
By increasing the material's glow past the limit, the bloom is "activated" by it sooner, making other bright things in the scene less bright by comparison. So those other objects shouldn't glow anymore. Set the object's glow really high, past the limit, then play around with those bloom settings again.