Friday, 3 August 2012

Daylight

The challenges of shooting in direct sunlight can be at times hard to overcome but with the right equipment and techniques, it can be a very rewarding process. So let us examine a bit closely the properties of light that we broadly address as daylight. The quality of daylight can be dependent on the prevailing weather conditions in the area. Many a times, conditions that amateurs would probably reject as unsuitable for photography can produce very dramatic lighting.

The word daylight has a clear definition in photography. In photographic terms, daylight is the average summer sunlight as measured at noon in Washington, DC, USA corresponding to a colour temperature of 5500K. This was chosen as the industry standard because these measurements were already recognized by the US National Bureau of Standards.

So adhering to the standards, photographic film manufacturers made colour film which was fine tuned to a colour temperature of 5500K and which will expose to give neutral whites when used between 10 am in the morning to 4 pm in the afternoon.

Thus Daylight film, or daylight white balance on a digital camera, defined a quality of light in the value of 5500k.


daylight
Photo By Freebird


Is daylight and sunlight the same?


Contrary to popular belief, Daylight is not the same as sunlight. Sunlight is light coming directly from the sun. But daylight is a mixture of sunlight plus light that is reflected from the clouds. This is the reason why we get a blue hue to shots taken during a cloudy day. During an overcast day, only very little sunlight passes directly through the cloud cover, most of the light reaching earth will be the light reflected back by the clouds overhead and thus has a bluer tone to it.

For example try taking the picture of a large tree in the middle of the day, the portion of the tree and surroundings which receive direct sunlight will be of a slight yellow tone and the portion of the tree which falls in shade (region under the canopy / shade of tree) will be actually illuminated by the reflected light from the clouds. So it has a bluish tone. So in the same frame now we have sunlight and daylight. This is one reason why there are separate pre-sets for colour temperature settings “daylight”, “cloudy” and “shade”. All these light have different properties thus separate pre-sets.


daylight - sunlight
Photo By Dimit

For photographers who wish to capture their images in daylight, it is important to have a thorough knowledge about the behaviour of sun. Although many are not aware of it, it is actually possible to predict the time of sunrise and sunset, how high will the sun be etc. right down to the specific day of the year. In order to do this prediction yourselves, you need either a pocket sun compass or a sun table.

A sun compass is a magnetic compass marked to show where the sun will rise and set at any time of the year. Once aligned, this shows the direction of the rising and setting sun for each month. And it has a second scale that shows the maximum height the sun will reach in the sky in any given month. Photographers use sun compass also to predict if the sun will clear a particular feature for example a tall building in the frame on a given time and day.

Sun tables are published charts that give the direction and elevation of the sun at any time of day throughout the year. Sun tables are more important for photographers who do architectural photography rather than landscape photography.

In the next article we will discuss about Photography - Types of Light - Morning Light

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