The purpose of this exercise is to increase your familiarity with histograms by relating each one to the image you have just shot. This is an aid to recognising the most basic characteristics of an image. Histograms appear twice in a normal workflow – the first time on the camera’s LCD screen, the second when the image is being processed – and it is valuable to make use of both occasions.
The objective is to shoot the three most basic categories of scene by contrast – low contrast, average contrast and high contrast – with three images of each; an average exposure and then one each at one f-stop higher and lower.
For low contrast the graph will have a concentrated area of low tones, for average contrast a reasonably even spread across the range of tones and slightly higher peaks and for high contrast large, wide peaks. If the image is under exposed, the graph will be grouped to the left hand side. Fo over exposed it will be grouped to the right hand side. For average exposure it should sit somewhere in the middle.
Above is an average low contrast exposure. As you can see, the graph is mainly grouped in the middle, if a little under exposed. However, my camera read this as correct exposure.
Over exposed results in the graph moving to the right, as expected.
Under exposed has shifted significantly to the left, as expected.
With a low contrast, the graph is fairly minimal peaks.
For a medium contrast, their are more peaks – this is expected. At correct expose its grouped in the middle.
When over exposed it shifts the the right.
When under exposed, it shifts to the left.
For a high contrast image the peaks are much higher and wider. Again, at a correct expose they are grouped in the idle of the graph. They are not ‘clipped’ on either side.
For over exposed (even slightly like in this image) the red and yellow bars are clipped at the right. Resulting in spacing at the left – meaning over exposure.
Again, the graph is grouped far to the left for under exposure.
All in all, this exercise produced results I was expecting. A histogram is a great way of adjusting camera settings to get the most accurately exposed photograph.