“Set your camera to any of the auto or semi-auto modes. Photograph a dark tone (such as a black jacket), a mid-tone (the inside of a cereal packet traditionally makes a useful ‘grey card’) and a light tone (such as a sheet of white paper), making sure that the tone fills the viewfinder frame (it’s not necessary to focus). Add the shots to your learning log with quick sketches of the histograms and your observations.”
For this exercise I used A4 black and white cards and the inside of a cereal box. Unfortunately, the cereal box had a number of creases in it which can be seen in the images. However, I decided that this did not detract from the aim of the exercise and I would still be able to demonstrate the exposures for each shot.
The three above images were taken using a Canon 5D Mk 3 on semi-automatic using Aperture priority. I originally set my camera to fully automatic mode and the camera could not focus which confused me at first. I posted a query onto the OCA blog as to why this should be and then on reflection realised that it was because there were not enough tones in the shots to help the camera focus. I received a number of helpful replies which confirmed this so I first of all took the auto focus off and then set the camera to Aperture priority.
As predicted and described in the course text the camera exposed for all three cards in the mid tone. This is described in the histograms and the similarity of tone in each of the images.
“Set your camera to manual mode. Now you can see your light meter! 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.”
Grey cereal box card
The creases on the cereal box are clear in these images. However, the histogram shows that the shutter speed of 1.3 seconds is probably the better exposure of the two shots.
These two images are both taken with the same aperture and ISO but with a longer exposure of 6secs in the first image compared to 1.6 secs in the second. Although the histogram is well to the right in the longer exposure there is no loss of detail and the highlights are not blown out producing a closer replica to the white card than the second image. The shorter exposure although not on 0 of the light meter is clearly beginning to move towards the mid-tone.
With the black card I opened up the aperture to it’s widest setting and increased the ISO to 400. Although not quite so clear on this resolution, in light room the 1/8 sec exposure looks more grey than the longer exposure. As seen in the images of the white card the histogram is close to the edge but there appears to be no loss of detail and the darks are not blown out.