Adding atmospheric perspective with a simple bluish ’color layer’. The value of this effect was applied (by masking) depending on the distance of certain objects.

First layer of fog. This was painted with a brush that leaves a cloud-like or smoke-like mark on the ’canvas’.

Second layer of fog.This is a duplicate of the first layer of fog with a bit of a blur added to it. This softens the whole ’fog effect’ in certain areas.