Apply dither after combining when conversion is made to uint8 to avoid banding

[FransBouma]

Prod80:

you could do something similar in your DoF shader... just use 16F textures until you go for output and after combining the blurred textures apply a dither to it... then when it goes for output and is transformed back to uint8 it is rounded and the dither is applied there automatically due to the minor variations applied by the gaussian noise texture. It's very cheap, easy to implement, and results are great.