Thursday, 4 October 2012

Exercise 34 Tungsten and fluorescent lighting

The initial requirement to establish light levels around a room lit by tungsten lighting was addressed by setting the camera to ISO100, using an aperture of f/4, and metering at various points around the room including directly at the lights themselves.  Shutter speeds set by the camera varied between 1/30sec and 1sec, all values that would have been unsuitable for hand held shooting without increasing the ISO value, using a tripod or both.  Of course, it does depend whether one was intending to shoot a static scene or a subject with movement as to whether a very slow shutter speed with the tripod was appropriate.  It was certainly very clear that the perception of the difference in light intensities from the eye were a great deal less than was metered by the camera.

At a time when the light levels outside from natural daylight and inside from the tungsten lighting were approximately equal, I took three images from a position where both indoors and outdoors could be seen.  These were with the camera set to auto, daylight or tungsten white balance.  I thought that auto gave a reasonably balanced view of the inside and outside although there was a stronger reddish tone to the inside than was apparent by eye.  Daylight rendered the image with a lurid orange which also impacted on the colour of the outside (at least it does in the large version).  The tungsten setting gave a cooler tone to the image and introduced a bluer tone to both the inside and outside and also gave far less saturated colours than either the auto or daylight settings.  Overall, I would say that tungsten gave a better photograph, especially of the tungsten lit interior, although if this image was to be used for anything I would certainly adjust the colour temperature and tint in post-production.
Tungsten :  shot in auto
Tungsten :  shot in daylight
Tungsten :  shot in tungsten
Finally, two situations lit by fluorescent lights were identified and shots taken with the camera set to fluorescent and auto and the photographs compared.  The first pair, a laboratory scene, showed the cleaner looking and slightly greenish blue cast obtained at the fluorescent setting and the second a dull and muted image from the auto setting.  The second pair was a corridor lit by fluorescent tubes and again the result was the same as the lab shot.  Neither pair of images was pleasing to the eye as far as the colour cast was concerned and all would have required adjustment of the white balance in post-production if they were required for use.  This occurs because fluorescent strip lights do not emit the full colour spectrum, although tubes can be bought which claim to be ‘daylight balanced’ and aspire to achieve this.
Fluorescent :  shot in fluorescent
Fluorescent :  shot in auto
Fluorescent :  shot in fluorescent
Fluorescent :  shot in auto
This exercise was interesting mainly because it made me more aware of the shortcomings of the camera white balance settings and reassured me that my usual workflow of shooting in auto and making white balance adjustments in post-production was a valid strategy under most circumstances.

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