Histogram. What it is and how we can use it?

You often saw this “histogram” when editing a photograph in, for example, Photoshop. Or you saw it on your camera screen right near your photo. Some of you might of ignored it, others even asked themselves but thought that it’s not that important to know.

Well, histogram it’s a powerful tool in digital photography because it can tell you whether or not your image has been expose properly, it can tell us whether the lighting is flat or harsh.  It will not only improve your skills on editing on the computer, but as a photographer as well.

Let’s start from the beginning for a deeper and clear understanding. An image is composed from a combination of the primary colors: red, green and blue. Each color has different levels of brightness measured in values between 0 and 255. So a histogram is composed of the number of pixels on each level from 0 to 255. Here is an example on the left.

In fact the histogram represents the tonal range of an image (the black region). Every image has different tonal range so you could say that there is no ideal histogram. So you as a photographer should have to make sure that the histogram represents what’s in the picture.

Here is another example of how colors and different levels of brightness are represented in a histogram. This is just a representative example not an accurate one.

So how can we use these histograms?

Well there are 2 different types of photographs High key and Low key photographs:

1. High key images are the photos where the predominant colors are very bright and there’s a lot of white also. (for example when we photograph snow, or landscaped with a lot of snow in the frame)
2. Low key images are those images where there are a lot of shadow areas dark colors in general ( for example when you shoot  your room and the windows and outside of them are correctly exposed but the inside are pretty dark)

The ones in which we encounter the most problems are the High key photographs. Why is that? Because if you shoot the snow with your camera set on auto you will se that the snow will not look white but more of a grey. That’s because the camera tend to put all the brightness levels in the middle so that the exposure is correct. In this case all the whites from the snow will be dragged into the middle so the whites will become gray. That is why when you check you histogram in you camera you will know that on the monitor you photo will look grey so you bump up you exposure so the the picture will come overexposed a little but the white of your snow will become very beautiful.

Some examples of High Key and Low Key photos.

Tags: Brightness/Contrast, Histogram, Photography, Photoshop