Ambient light is existing natural or artiﬁ cial light present in any environment. Ambient light can be subdivided into four major categories:
Daylight is a mixture of sunlight and skylight. Sunlight is the dominant or main light. It is warm in colour and creates highlights and shadows. Skylight is the secondary light. It is cool in colour and ﬁ lls the entire scene with soft diffused light. Without the action of skylight, shadows would be black and detail would not be visible. Most colour ﬁ lms are calibrated to daylight at noon (5500K). When images are recorded at this time of the day the colours and tones reproduce with neutral values, i.e. neither warm nor cool.
A common type of electric light such as household bulbs/globes and photographic lamps. A tungsten element heats up and emits light. Tungsten light produces very warm tones when used as the primary light source with daylight ﬁ lm. Underexposure occurs due to the lack of blue light in the spectrum emitted. The orange colour cast can be corrected with a blue ﬁ lter if neutral tones are desired; however, correct colour can be achieved without ﬁ ltration if used with tungsten ﬁ lm. Digital cameras neutralise colour casts introduced by light sources other than daylight by adjustment of the white balance to the dominant light source or by capturing as RAW format and correcting in post production.
Phosphors inside ﬂ uorescent tubes radiate light after ﬁ rst absorbing ultraviolet light from mercury vapour emission. The resulting light produces a strong green cast not apparent to the human vision. If used as a primary light source the results are often unacceptable due to the broad ﬂ at light and the strong colour cast. Underexposure is again experienced when using this light source and the cast can be difﬁ cult to correct. Fluorescent light ﬂ ickers and causes uneven exposure with
focal plane shutters. To avoid this shutter speeds slower than 1/30 second should be used.
Light from naked ﬂ ames can be very low in intensity. With very long exposures it can be used to create atmosphere and mood with its rich red tones.