Basic Techniques | Dynamic Range and Histograms

Throughout today's post I am going to explain what dynamic range is and how it is displayed through the use of a graph known as a histogram. 

What is Dynamic range?

The dynamic range of a photograph is captured by the camera sensor and it describes the ratio between the maximum and minimum measurable light intensities, which basically refers to the brightest objects in the scene and the darkest objects in the same scene. Our eyes have a high dynamic range as we make bright things, and dark things appear at fairly the same brightness, a camera however cannot do this. The examples below, which I found on another site can be found here.

This is how our eyes would view the scene as we have a high dynamic range....

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And this is how our camera would view it, it would need to take two exposures, one to underexpose to capture detail in the highlight, and one to overexpose to capture details in the shadow areas.

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It's quite confusing and very difficult to get your head around, I hope i've managed to explain it okay here?

What is a histogram?

A histogram is a type of graph that shows you the dynamic range of the image by displaying how many pixels there are at each level between black and white, black is the left hand side and white is the right. The height of the graph depends on how bright the pixels are at each point. (Once again, I found another useful site here with a more in-depth discussion and some great examples.)

Here is an example of what histograms look like representing the dynamic range of the photograph.

This first histogram is for a shot of mine that is over exposed. As you can see, the histogram is pushed up to the right.

 

This one shows an underexposure of the same scene, and the histogram quite clearly appears more pushed up to the right handside.

When they are pushed up to the side, this results in clipping, which means any information pushed off the graph cannot be retrieved. Any detail in these shadows and highlights will be lost.

Try and achieve histograms where the graphs falls back to the bottom before it runs of the edge, similar to these examples from images of mine below...

I hope this post hasn't been too confusing and I hope you've been able to get a better understanding of these important photographic topics.

Thanks for reading!