Good Examples of Exposure

[[Geoff Slocock]]

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As a matter of fact there are tweaks applied here.

But just for the moment I don't want to say what they are; and some discussion can follow where this felt to be useful.

Good exposure is on the eye of the beholder, too. So what I have done in selecting my example is choose according to my taste.

[Spike]

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This is a photograph of the Signal Tower Museum in Arbroath. Photograph is straight out of the camera, but the histogram suggests that it is properly exposed.

Spike

[[Geoff Slocock]]

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Spike, this is an adaptation using the Gimp and Colors > Levels.

Let me first explain my interpretation of the histogram. The peak on the left shows the pixel count for the lighter areas of the picture (sky, magnolia-coloured walls, and sodium lit areas). The peak on the right represents the grass and slate areas. The middle peak represents the mid-tones and here they are grey and paler green areas. (This is where a little knowledge of how colour tones convert to greyscale helps).

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What I did was to pull in the left slider to A and the right slider to B. You see this shot is well exposed because every part fits well within the camera sensor's available dynamic rage. However, to optimise it some more you need to close those blank areas on the left and the right. Doing that sort of "stretches" the dynamic range of the taken picture. Here again are the before and after shots. What do you think?

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Of course, your shot is superb. But you understand histograms and the LEVELS command is an easy tweak to do once you understand histograms. BTW, the middle slider controls brightness levels of the shot.

[Spike]

Geoff I think you have made a big improvement. Went on to the Gimp just to see for myself how it is done and it seems easy to change the photo for the better, but I guess the hard bit is knowing what to change in order to improve the photo.

Spike

[[Geoff Slocock]]

The histogram is there in the camera and is present throughout post processing and it is seriously used. But it scares folk, and also from the beginning most of us try to use just our eyes to judge the quality that we want.

The LEVELS command is applied to the zero tone-presence end-zone regions and is easy enough to apply, in order to collapse those data-empty end-zones.

As I have mentioned also the standard histogram is based on a monochrome conversion and that means that you as the user need to understand a little of how coloured tones translate on the greyscale range. In many ways, too, dynamic range within a shot is more easily understood with reference to the converted greyscale form of a picture.

So one observation that can be made is, yes, use your eyes but also use the histogram. It will provide important information that is based on collated data from the totality of the pixels, and not merely personal judgement.

Getting good in doing that is partly about watching good instructional videos and it is also about going through some regular learning-type check-lists when taking and processing photographs.

Some folk will of course take a CAN'T DO attitude, saying they don't understand and never will understand. But certainly the use of the LEVELS command can be very dramatic in the way that it improves the range of tone in a shot and give a subjective impression of something like sharpness or contrast, or put more simply just makes everything stand out more.

But I guess, also, these histogram-based techniques lets you be rather in more in control of your pictures.

[[Geoff Slocock]]

[center][block]The Cambridge In Colour Histograms Tutorial[/block][/center]

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I have just read this through again and I first read it three years ago. I guess, I kind of knew, back then, that I would not really understand all the points made that easily. And I would say now that I have had to pull in all sorts of other acquired experience.

If I go on an excursion in my daydreaming mode and observe that if I were now sitting for finals exams in a photography degree course, I could make preparation: I could devise specimen questions and prepare to answer them, I could examine aspects of this article and come at those aspects in different ways.

And I am being honest with you, when I take off on my daydream, because when you start out you should not endeavour to take any sort of comprehensive or all-seeing view of it all. But indeed as you make progress you can start to see the bigger picture.

So I commend giving this article a read, because it will start to give you a picture of the "bigger view".

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Now for a bit of light relief.

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My degree was in Mathematics, Statistics and Computing. And this explanation rings bells with me. However, note that the guy calls a histogram a "statistical" tool. Normally, however, you make a histogram for representing sampled data; but here the data from the camera is seemingly not sampled from some bigger population. No it is the TOTAL set of data, for that particular picture.

But think again of all possibilities of pictures that could ever be taken. Then your particular picture is just one particular sample. So it is in this sense it is a statistical method; and I am sure (in my own mind) that a tone histogram will be better understood if this aspect is not dumbed down.

But, again this may not be at all helpful for you, as an entry point and there lots of other videos on YouTube that you can look at.

[Spike]

Thanks Geoff, I need to do a bit of work to better understand histograms, and the tutorial and video above are already a big help.

Spike