Set your camera to any of the auto or semi-auto modes. Photograph a dark tone, a mid-tone and a light tone. Add the shots to your learning log with quick sketches of the histograms and your observations.
What an interesting exercise. I guess I must have realised intuitively this is how the camera works out exposure. But nevertheless if I had been asked how the histograms would appear in these three scenarios I would’ve got it wrong! And I would have expected the images to be white, grey and black. Good lesson learned then!
Set your camera to manual mode. The midtone exposure is indicated by the ‘0’ on the meter scale with darker or lighter exposures as – or + on either side. Repeat the exercise in manual mode, this time adjusting either your aperture or shutter to place the dark, mid and light tones at their correct positions on the histogram. The light and dark tones shouldn’t fall off either the left or right side of the graph. Add the shots to your learning log with sketches of their histograms and your observations.
To gain the correct histogram positioning for the white, grey, black shots I simply adjusted shutter speed to 1/20, 1/40 and 1/10 respectively. The white and black settings were as expected. But to ‘centralise’ the grey histogram I needed to set the shutter at 1/40. I would have expected it to have been more like 1/15! Perhaps it just wasn’t a great grey card!