Thursday 1 October 2009

Measuring the Intensity of Light

Brightness varies between dusk and dawn. The sun seems brightest at midday when it is highest in the sky. At sunrise and sunset its light has to pass through thicker layers of atmosphere and so appears dimmer. Clouds, haze and mist also darken it.

The requirements of this project were to make a series of readings throughout a sunny day from early morning to evening and create a graph with the results. I spent the 23rd of November taking measurements with my light meter and recorded the results in excel. Being winter in Mnchester its very rare to have a sunny day, I did my best to choose a day that wasn't too dull. Below are my results.

I set the shutter speed to 1/125th of a second and my meter told me the appropriate f stop to use while shooting each time I took a reading. The sun was at its highest at 8:50 and so the f number stayed constant until the sun began to set at 15:00.


Graph of resultsIndoors the light would be dimmer and therefore the a wider aperture (lower f stop) would be needed than outside. During the summer the sun would be brighter and in the sky for longer. The f stop would need to be higher for a longer period of time.