Hi Slavq,
The issue here isn’t the emissivness, but instead it’s a post process issue with Bloom. Since the post process is screen space oriented the smaller the object on the screen the smaller the effect. When TXAA is enabled it’s blending with the previous scene to smooth the result which can reduce the amount of bloom shown at further distances. You can adjust the Bloom Settings in the Post Process to get better results at further distances, although you would probably need to adjust the threshold to reduce other objects or lights from producing too much bloom as well.
I hope this helps.
Tim