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).
|
|
Fig.11 The results of setting the white balance to compensate for differing uncorrected light sources. |