Mixing
Artificial Light With Daylight
When using a combination of artificial and natural light, whether
the location is exterior or interior, one or other of these light
sources must be colour corrected. However, this does not always
apply if the artificial light is being emitted at daylight colour
temperature. Examples are some studio fluorescent lights, arc lights,
and HMI lights, none of which are incandescent lamps. The exception
to this rule is that most industrial and domestic fluorescent tubes
will require correction or turning off.
If the natural light is strong, and is being used as the key or
modelling light, it is important to consider that once filters are
added to your artificial lights they may not have enough light output
to achieve the desired lighting effect. Also be aware that sunlight
is constantly moving, and liable to become masked by buildings,
trees or clouds.
You should never attempt to use the camera's white balance to compensate
for differing light sources. Fig. 11 shows the result of a set-up
that comprises a daylight modelling light, fluorescent ambient light
and a halogen fill light. The above lighting can produce a green
hue with purple in the shadows and this may not be noticed until
the edit stage.
On outside locations most HMI/arc lamps will need little or
no correction, but halogen lamps will need to be filtered with a
blue or half-blue, dependent upon the amount of colour correction
required; this can vary throughout the day. Imagine that you are
shooting a piece to camera (a talking head, as it is often referred
to). In a typical exterior set up, if it were a very bright day,
you would use the daylight as your modelling light, and your Paglight
as a camera-top fill-light. In this situation, you should use the
blue Dichroic Filter (Model 9951) in order to raise the colour temperature
of the halogen lamp to match daylight.
The sacrifice will be a slight loss of light output, but this is
preferable to having a colour mismatch. Alternatively, you can use
the Paglight PowerArc (Model 9955), which operates at daylight colour
temperature without requiring any colour correction. Using the Diffuser
(Model 9952) you would then adjust the beam angle to balance the
contrast range between the lit and shadowed areas of the subject.
- Try not to let the fill-light become the
predominant light.
- Fill light should always be soft, so it
is advisable to use
the flip-down diffuser, especially in medium to close-up shot
situations.
- For super-soft lighting use the Softlight
Diffuser and Filter Kit (Model 9983). This kit works as a stand-alone
item, or in conjunction with the Diffuser to give a very flat,
super- soft light spread from the larger illumination area.
This kit is perfect for medium to tight close-up facial shots.
If you are working
inside you can fit gelatine filters to the windows to convert
the incoming daylight to artificial light. This would normally
be a 204 Full-CT-Orange, a Half 205 or a Quarter 206, dependent
on the correction required. Having done this, the view out through
the window will look normal to the camera, provided that the light
outside does not overpower the lighting within. If this is likely,
measure the difference with a standard light meter and chose a
Full-CT-Orange 207 with +3 ND or 208 with + 6 ND content, reducing
light by 1& 2 stops respectively. Filtering in this way enables
standard halogen lamps to be used without filters, effectively
increasing their output.
Interestingly, any
person working within such a room for a reasonable time would
gradually become accustomed to the shift in colour and be unaware
of this fact until removing the filter from the window or stepping
outside, where for a minute or so everything would appear to have
a positively blue tint to it, even white sign boards. You would
also observe the effect gradually diminishing as the brain readjusted.
This is further proof that the human eye can only detect differences
in colour content by direct comparison, and this is the reason
why the discerning professional uses a colour meter to aid his
work.
In any swift set up, where time is limited,
filtering windows may not be the most practical solution. The
only alternative is to 'blue-up' the tungsten lights with either
glass dichroic filters, which can be placed in the filter frame
behind the barndoors, or larger gelatine filters. Gelatine filters
are cheaper than dichroic but must be set out from the front of
any light and away from the heat.
The choice is Full-CT-Blue 201, Half-CT-Blue 202, or a Quarter-CT-Blue
203.
When using your PowerArc in an artificial
light environment you should use the daylight-to-halogen PowerArc
Filter (Model 9973). When working closer than two meters from
people it is good practice to use the Diffuser (Model 9952). This
can also be used in combination with all other correction filters
including the larger gelatine Softlight Diffuser & Filter
Kit (Model 9983).
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Fig.11 The results of setting the white
balance to compensate for differing uncorrected light sources. |