BACK LIGHT [Film Technology]

BACK LIGHT 
[Film Technology]

To create an illusion of  depth and substance, a back light is directed towards the camera on to the subject. Back light on to subject to help create substance by making it stand out from background. Light directed towards the camera on to the subject, to give depth and substance. While using sunlight as back light separates artists and objects from the background and gives character to the background lighting. If the light is moved to a position at ⁰12H directly behind the subject, the lamp itself is hidden and mostly effectual, although any translucent, fury, feathery edgings catch the light and stands illuminated-as when sunlight shines towards us through leafy trees. Light that falls up on a subject from behind a light shining towards camera. Fundamental purposes :  

1) It outlines part or all of the subject, forming a rim that tonally separates it from its background where dark clothing, for example, would merge into similarly dark background tones, such back lighting is valuable. 

2) It models the periphery of subjects, revealing edge contours. Thus although there may be sufficient tonal isolation so that a dark suit stands out from a light background (as a silhouette) only when back light catches its folds and reveals its shape will the material appear to have solidity.

 3) It can illuminate areas that fall in the key light’s shadow, and would be insufficiently revealed by fill-light. 

4) Back light enables the detail of translucent objects and tracery to be revealed.

Light from behind the subject usually illuminating its edges :

1)   The effectiveness of back light changes with its vertical angle. 

2) 

a) Back light rims the subject’s sides, to an extend depending up on its horizontal angle. The width of the illuminated rim broadens as the light moves from behind the subject towards a side position. Any subject contouring or protuberances (e.g. ears, hair) will cast long shadows forward over the side of the face when slightly offset back light is used these shadows shortening as this back light moves towards 3/4 back position. 

b) Combined back light produce double rim lighting which exaggerated, becomes a `badger effect’. Slight double rim lighting at the subject’s edges can produce a glamorous, attractive visual effect. If inappropriately applied, however, it can over emphasis head out lines (i.e. ears , coiffure) and apparently exaggerate head-width, neck thickness. The shaded center stripe effect that results from broadly angled double-rim or from side lighting is seldom appealing. If often arises in horse shoe group shots where cross light for facing speakers bisects a centrally positioned person. 

3) The direction of backlight may modify the apparent balance and width of the face. a) When the key is directed on to the narrow side of the face, the wider side may be visually narrowed by shading. b)When the key lights the wider side of the face, a back light on the narrow side rims it, effectively widening it. c) A back light on the same sides as the key will tend to nullify the key’s modeling and over light one side of the face. Increased compensatory fill-light would encourage flat results. 

4) The amount of backlight required by one subject may be less than the key light intensity for another nearby subject. 

a) Use separate lamps where space permits. 

b) Use a localized diffuser. 

c) Arrange a single lamp so that the key is fully positioned on the subject, while its beam edge fall-off serves to back light the other subject. Light shining toward the camera back lights the subject with a surrounding rim, revealing any transparency and separating it from the background.

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