Photographers can become obsessed by lighting, yet many of us ignore the effect the angle of the sun can have on the pictures we take. Most people know the best times for photography are early in the morning and late in the afternoon, and many are aware that the low sun angle produces elongated shadows, which lend definition to subjects. But sun angle can have other effects on the ways in which digital camera sensor records the tones in image files. Understanding these effects can not only help you to use your camera more effectively; it can also illustrate the value of having equipment reviewed in the lighting conditions that apply where you live.
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Photographers can become obsessed by lighting, yet many of us ignore the effect the angle of the sun can have on the pictures we take. Most people know the best times for photography are early in the morning and late in the afternoon, and many are aware that the low sun angle produces elongated shadows, which lend definition to subjects. But sun angle can have other effects on the ways in which digital camera sensor records the tones in image files. Understanding these effects can not only help you to use your camera more effectively; it can also illustrate the value of having equipment reviewed in the lighting conditions that apply where you live. Sun Angle You might think the sun is directly overhead at noon but, in truth, this only happens along the equator. Everywhere else, the sun may be at its highest at noon, but how high it is in the sky depends on how far you are from the equator and the season of the year. For example if you live in Sydney Australia, the noon sun is highest between 21 and 27 December, when it is just 10.5 degrees off vertical. In Darwin Australia, it’s less than two degrees off vertical (which is effectively directly overhead), but in Hobart the difference is almost 20 degrees. In the middle of winter, the altitude of Darwin’s noonday sun has slipped to about 36 degrees, Sydney’s is at around 57 degrees and Hobart’s is just over 66 degrees. Compare these figures with well-known places in the Northern Hemisphere and you may get a shock. In summer, New York has a slightly lower noonday sun angle than Sydney, while London’s latitude of 51.3 degrees north gives it a sun angle of 28 degrees off vertical, and the UK’s northernmost city, Lerwick, is almost 37 degrees off vertical. But in winter, the sun in New York rises just 25.9 degrees above the horizon at midday, putting it just over 64 degrees off vertical; London’s midday sun is almost 75 degrees off vertical and Lerwick’s is an amazing 83.5 degrees! (If you’re interested in finding out sun or moon angles anywhere in the world at any time of the year, there’s a neat calculator available at http://aa.usno.navy.mil/data/docs/AltAz.html.) Sunrise and, especially, sunset are very popular times for picture-taking because the lower sun angle produces longer shadows and the light is attenuated by the atmosphere (it has to pass through more air at lower angles), which produces the characteristic ‘warming’ of colours and tones and an overall softening of the contrast of the light. At these times, differences in sun angle of about 10 degrees are very obvious – and even a lowering of the sun angle to 45 degrees can reduce the intensity of the incoming sunlight by 30%, which can also make scenes less contrasty. If we take a 10-degree shift in sun angle across sunrise and sunset as indicating twilight, it’s interesting to compare the length of these periods in four places that represent different distances from the equator (latitudes).
* In mid-winter, the sun doesn’t rise above 6.5 degrees above the horizon during the 5ø‚ ½ hour days! Of course, there are times when the sun angle in all latitudes is the same. But these don’t necessarily occur at the same time of day and the closer you are to the equator, the briefer they are. Consequently, if you want to capture the colours of sunset in Darwin during summer, you have to act quickly, whereas in Hobart Australia you have longer to compose shots. Sensors, Contrast and Australian Conditions In many years of reviewing digital cameras, one of the distinguishing factors we’ve noticed about compact digicams is the comparatively high contrast their sensors deliver. This is probably due to a combination of two factors: local shooting conditions for our tests, and the way the camera’s image processing system has been set up. All digital cameras have been manufactured to meet the needs of the majority of buyers, most of whom live in the large population centres in Europe, Asia and North America – and in latitudes that are significantly higher, on average, than the major population centres in Australia. If you add to the natural light attenuation caused by sun angle the effect of the atmospheric aerosols (water vapour and pollutants) that are found in the environments in which these cameras are developed and tested, you shouldn’t be surprised if manufacturers choose to boost the image contrast a little to deliver more ‘punchy’ pictures. And it seems that process is taking place with the majority of compact digicams (it’s common for saturation to be boosted as well for the same reason). When you use these cameras in Australia, not only are our average sun angles higher, but our air is less polluted. Consequently, many digital cameras produce quite contrasty images when they’re used in bright outdoor lighting and it’s common to find that highlight and shadow detail are lost. The problem is more frequent in compact digicams than in DSLRs but, even there, the default settings in some entry-level models are slightly too contrasty. We take account of these factors when reviewing digital cameras and report when we find cameras with both wide and narrow dynamic ranges that could affect picture quality. Because of their locations, it is doubtful that overseas reviewers would be as sensitive to this aspect of camera performance, which probably explains why we seldom see comments on tonal reproduction in online reviews done overseas.
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