6.6.2 Bloom Filtering attributes

Post Effects tab in the Render Settigns Window when Iray Photoreal is selected
Bloom Filtering, sometimes referred to as light bloom or glow, is used to reproduce an imaging artifact of real-world cameras. The effect produces fringes (or feathers) of light extending from the borders of bright areas in an image, contributing to the illusion of an extremely bright light overwhelming the camera or eye capturing the scene.
Enables or disable the Bloom Filtering effect.
Sets the blur radius of the bloom filter, specified as fraction relative to the output resolution. As a rule of thumb smaller values create a local effect around bright areas of the image usually recognized as specular highlights.
Specifies the threshold to cut off bright spots in the image and blur these in a second step. As a rule of thumb higher values create more spottiness.
Brightness Scale
Scaling factor for the blurred bright spots when composited.
 Rendering with the bloom filter