Inverse Square Law – double the distance of the light source = 1/4 the brightness of the light.
If this calculation is correct i should be recording the same exposure value from different distances. Which means if i double the distance of my first measurements i should 1/4 the light source by moving my aperture 2 stops. This means 4 times as much light much be let into the sensor. Which means as the point source radiates outwards the light get weaker.
Today i photographed trip shots using inverse square law so that i can test the law to understand how light fades. I did this using Point sources of light. I photographed my subject using various lighting situations which were available through windows and lights, most of this was unavailable light to due the sun been behind the clouds, however at some points the sun was out which did affect my overall exposure throughout some shots.
I metered reflected light at 1 sec exposure.
– From the locations i photographed i discovered that many factors can affect the overall outcome of the image. Within the images i captured i expected to capture an image which was correctly exposed, then underexposed then an image with the same exposure value of the first image – if the inverse square law works. However i had many mitigating factors which affected this outcome. Lighting from above and around the subject also lit up my scene which caused the exposure measuring to capture odd results. As well as this the sun was in and out of the clouds within the shoots. Other factors include…
– size of point source and the angle of which it is entering the location
– size of model, clothing of model
– colour surrounding subject, can reflect/absorb light
– keeping model still for long exposure
Overall throughout these long exposures i discovered that inverse square law does not always work because to many factors of other light sources influence the scene. This is upon location whereby other light sources are close by and unavoidable. However this may be different under controlled, set studio lights.