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.
Add the sequence to your learning log with the time info from your camera’s shooting data as your first images for Part One.
The photos where all taken within a 3 second sequence of each other using a Nikon D5600. All on fully automatic with a 20mm focal length, ISO560, f4 aperture and 1/60th shutter speed, I never used a tripod but instead rested on the back of a chair to keep the images in frame.
Even with all the settings set the same and the frame almost identical in each photo the histogram still shows subtle variations in each individual picture.
As the test suggests what changes take place in such a short period of time, the variables are probably countless i.e. light shift, button depress, focal points. With today’s sensors no 2 photos can ever be taken with the same camera and produce identical histograms.