The task was to match six pictures to six histograms. I am familiar with the histogram, as I am well used to working with Levels within Photoshop. Resisting the temptation to peek at the answers, this is how I matched the images (n.b. I have asked on the forum whether it is permissible to post low-res copies of the actual images here, but as I'm not sure yet, I'd better not risk breaking any copyright laws, so it's the histograms only for the moment):
Histogram 1: Japanese Girl
The photograph includes a broad range of tones, and this histogram stretches right across the range, from dark to light. I believe that the large peak on the left corresponds to the almost black background, which takes up a comparatively large percentage of the image. The next peak most likely corresponds to the darker area of the girl’s kimono, and perhaps to parts of her skin tone. The next noticeable peak is likely to be the lighter area of the kimono, and finally, the small but sharp spike on the extreme right corresponds to the bright highlight on the hat (part of the decoration on object she is carrying).
Histogram 2: Carmen
This was one of the more difficult images to match up with a histogram, and I initially thought that this graph belonged to the white magnolia. However, I then noticed that there are some pure blacks, which do not exist in the magnolia image. The histogram fits the Carmen image more closely. There is a peak of pure black, which could correspond to the darkest area of the background, to the creases on the man’s sleeve, or to the shadowed part of the woman’s hair. Moving from left to right, there are then two large peaks, the first of which corresponds to the majority of the background.
The second peak corresponds to the man’s jacket, their hair, and parts of the background. The histogram is then relatively flat, rising very slowly towards the lighter end of the scale. Then, on the right, is a series of peaks, one of which is very steep. The steep peak most likely corresponds to the lightest areas of the woman’s dress. The smaller peaks match the slightly shadowed areas of the dress, the man’s shirt, and their skin tones.
Histogram 3: Bluebells
I found this one of the easiest images to match to a histogram. The tonal range is limited, with no pure blacks or whites. Contrast is low, and the histogram reflects this. The graph does not touch either the left or the right end of the scale. Instead, there is a large peak in the middle, which corresponds to the mid grey tones that make up a large percentage of the picture. The low level of lighter tones, to the right of the histogram, correspond with the lighter areas on the leaf at the bottom right and a comparatively light area of background about a third of the way up on the right-hand side of the frame. The small amount of dark tones, as indicated by the histogram, correspond with the darker shadowed areas of the flowers.
Histogram 4: Pyramid
As with the bluebell image, I found this one quite easy to match, as there is a concentrated tonal range. The overall impression of the image is that it is dark, which corresponds to the histogram, The graph shows the tones clumped together towards the darker end of the scale. The graph almost touches the right-hand side, this represents small dark areas on the lighter face of the pyramid. Moving from left to right, the first small peak corresponds with parts of the shadowed area of the pyramid and the distant hill. The image is very ‘noisy’, therefore this peak could actually be made up of many individual pixels, rather than a specific area of the image.
The next large peak represents the bulk of the image – the remainder of the shadowed areas, sloping down to parts of the ground – the pebbles, then the rippled sand. The histogram continues to slope downwards, covering the sky and some parts of the pyramid. Finally, a thin line stretches out to the right-hand side of the graph, representing the highlighted areas – parts of the entrance to the pyramid, an area of ground touching the right-hand side of the frame, and the bright spots of the stars in the sky.
Histogram 5 – Oil Flask
This item has been isolated on a white background, therefore it was immediately apparent that its histogram would show a peak on the extreme right. There is a second sharp peak slightly to the left, which corresponds with the light grey colour of the body of the flask. A third, smaller peak corresponds to the table upon which the item is sitting, and the flat, thin line that stretches towards the left edge of the graph corresponds to the darker areas of the object.
Histogram 6 – White Magnolia
As mentioned above, I initially matched this up with histogram no. 2. However, a closer look at the image showed me that there were no black tones – in fact, even the darkest area of the picture is a distinct grey, rather than being even nearly black. Closer examination of the histogram showed that there was a peak flat against the right-hand edge. This corresponds to the burnt-out highlights on the petals.
Moving left, the next significant peak corresponds with the light grey areas of the petals, then the tall peak in the centre represents the more or less uniformly ‘mid grey’ background. The smaller peaks to the left of this represent the shadowed areas of the leaves, and the small amount of darker tones match up with the darker stems and darker shadows on the leaves.
Upon checking the answers, I found that I'd got them all right - yay! It was a close call with the magnolia and the Carmen image though, I very nearly got them the wrong way around.
What have I learned from this exercise?
I've learned that I've got a fairly sound understanding of the histogram, and the way that it represents the tones within an image. However - whether I would have found it so easy if the images had been in colour, I don't know. This has helped me to consolidate my knowledge of this area. Although I 'knew' what the histogram represented, I have never looked at them in detail in this manner. In this respect, it has been very useful. 
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