Take three or four exposures of the same scene. Don’t change anything on the camera and keep the framing the same.
Preview the shots on the LCD screen. At first glance they look the same, but are they? Perhaps a leaf moved with the wind, the light changed subtly, or the framing changed almost imperceptibly to include one seemingly insignificant object and exclude another. Time flows, the moment of each frame is different, and, as the saying has it, ‘you can’t step into the same river twice’.
Now bring up the histogram on the preview screen. The histogram is a graphical representation of exposure – the camera’s sensitivity to light. As you page through the images you can see small variations in the histograms. Even though the pictures look the same, the histogram data shows that in a matter of seconds the world changes, and these subtle differences are recorded by the camera. If you refine the test conditions – shooting on a tripod to fix the framing, moving indoors and closing the curtains to exclude daylight – still the histogram changes. Probably some of the changes are within the camera mechanism itself; still, the camera is a sensitive enough instrument to record them.
Whilst thinking about this exercise my mind wondered to the original meaning of Photography, which came from the Greek word ‘phótos’ and ‘graphé’, translating to ‘drawing or painting with light’. Not only are you capturing a moment in time, but you are also capturing the light at that precise moment.
The above set of photographs were taken one second apart. They show that within a second the scene can dramatically change. As the wave moves towards the foreground and gets larger, the histogram subtly starts to move towards the highlights. By capturing a wave crashing against the rocks, I wanted to demonstrate that you are capturing a moment in time that will not be repeated again. As the Brief says ‘you can’t step into the same river twice’. The next wave to come in will not crash against the rocks in the same way. The light will have also changed and because the wave and spray will be different it will capture and reflect the light differently too.
For my second set of photographs I chose to photograph a lava rock wall which was outside but under cover, knowing that there would not be any physical movement of the object. By using a neutral coloured wall I wanted to demonstrate that the light a photographer captures is constantly changing.
After reviewing the histogram, I noted that although the peak of the Histogram is set within the Midtones it shifted ever so slightly towards the shadows on each photograph. At the time of taking the photographs a cloud was moving over. Due to different densities within the cloud the light increased and decreased creating a difference in the amount of light being reflected. The camera changed the shutter speed from 1/30 to 1/40 in order to compensate for the change in light. However when you review all three Histograms you can see that despite the camera making an alteration to the shutter speed in order to achieve what it thinks is a ‘correct exposure’ each Histogram shifts slightly towards the shadow end.
Following the photographs of the wave and wall, I decided to take three consecutive photographs fully out in the open to demonstrate the effects of movement and light a little more subtly.
Although all three photographs look the same, upon closer inspection there is a difference in the intensity of the shadow cast by the palm on the lava rock wall. This is most noticeable in the third photograph. At the time of taking the photographs there was a gentle breeze, and although it is hard to spot some of the palm leaves moved a fraction.
I shot all photographs in RAW. RAW files naturally contain an amount of noise, which I have not corrected as this would alter the Histogram. The amount of noise within the photograph may explain the broken comb effect on the Histograms.