How to Understand Histograms and Get Better Images

 

A very useful tool found on most cameras today is the histogram.

 

What is a histogram and why should I be interested?

 

A histogram is a graphical chart which shows areas of brightness on an image (or tonal values) which ranges from pure black (left-hand side) to pure white horizontally (right-hand side), and the number of pixels vertically.

 

This all sounds very technical but with a little bit of practice you can tell straight away whether an image is overexposed or underexposed.

 

Needless to say, with a digital camera the option is there to make an instant adjustment and get a better image.

There is no such thing as a "perfect" histogram.

 

Some scenes have a predominance of dark or light tones but for a typical well-balanced scene showing both dark and light tones you should expect to see a curve which starts at the bottom left-hand corner then slope upwards to a peak somewhere in the middle then descend to the right-hand corner.

 

This will indicate a wide spread range of tones, or a wide spread of light and dark.

 

However, if a histogram shows a curve which starts somewhere up the left-hand side and finishes at a point somewhere on the right-hand side, looking as if it has been cutoff abruptly at both ends then this might indicate under or over exposure.

 

Conversely, if the curve starts and finishes on the bottom axis but not necessarily in the corners there should still be a full range of tones. Generally speaking, controlling highlight detail tends to be more important than controlling shadow detail.

 

If the histogram is weighted towards the right-hand side then blown-out highlights may be present and the necessary adjustments can be made to adjust the exposure.

 

Suffice to say, if the shadow detail is more important then the opposite occurs. To sum up once you become experienced at "reading" a histogram you'll be able to almost instantly evaluate the quality of the exposure that the camera is making.

 

This is especially true when the histogram is superimposed on or just next to the image itself, which you can find on many cameras, making the graph that much more meaningful.

 

Remember there is no such thing as a "good" histogram. The histogram shows you how it is and leaves you with the options to adjust this.

 

I thoroughly recommend that you take a look at this excellent aid to better photography. It is the work of seconds to look at the histogram at the same time as you look at the image you have just taken. You will soon begin to recognise what is a "good" image for you, at that time, and whether you need to adjust exposure,and try again.

 

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