Hola amigos! Probably many of you already know this technique; The Day-for-Night or American Night (as it’s known in Europe) is a cinematographic resource which consist in simulating a nocturnal recording in broad daylight. I also seize this opportunity to recommend Françoise Truffaut’s Day for Night (1973) which revolves around this technique guided by one of the biggest exponents and father of the french Nouvelle Vague.
This technique was popularized in Hollywood, making his peak on western age as a way to deal with the complications and costs of night shooting. One example of it is The Searchers (1956) by John Ford. The effect is as simple as playing with light and color parameters on our camera:
First of all, despite it is possible simulating night on daytime, it is not recommended shooting exposed to direct sunlight as it can create awkward sharp shadows which are not realistic for the moonlight as light is more diffused at night time. The best option is shooting on a cloudy day.
We can choose parameters on our camera having in mind we are shooting a night scene, so low ISO and closed diaphragm are the best option. The subexposition of the light is the key of the technique, around -2 F points should be enough. We can use Neutral Density Filters instead, which diminish the light without color alterations.
The following steps are related to color: Despite moonlight is not blue, our vision perceives it like It was. This is because of Purkinge Effect: Our eyes tends to shift into blue light in low light situations.
The color temperature in outdoors is 5000 Kº, while it is 3300 Kº in indoors. A White Balance balanced to tungsten will give us a bluer appearance and turn artificial light into “moonlight” sensation.
Depending on whether recording B&W or Color, We must use a CTB or CTO filters on the objective, which erases specific color frequencies; we will use CTB for Black and White and CTO for Color. This is because CTB on B&W will make the sky look darker while CTO on color will cool the light. This is an example of what we can get by using this technique. Have fun!