Day-for-night photography is an effect that makes a scene recorded in daylight to appear as if it were at twilight. This is usually accomplished by the use of a filter that both underexposes by about two stops, and can also produce a bluish color overcast. Lighting, contrast, and other factors contribute to the reality of this effect.
Tiffen offers the Cool DFN filter, which is a lavender- blue color traditionally associated with dusk or twilight emulation with day-for-night effects. Day for Night Filters require an additional underexposure by ? to 1-1/2 stops above not compensating for them in the first place. Advance testing is recommended.