Basic Histograms

Every digital camera these days includes a basic histogram display as an addition or option to the preview image on the LCD.  The histogram is a VERY useful feature to judge exposure.  There are several components to a histogram and in future columns we’ll cover all of them in depth, but this weeks lesson will cover a very basic view so you can immediately start to use your histogram to achieve more accurately exposed images

Please keep in mind that there is much terminology, camera mechanics, and the such to cover before you can understand everything there is to know about histograms, but for the purpose of this weeks column we’ll assume you can look in your cameras manual and learn how to use  “exposure compensation” to vary your exposure within the automatic program mode.  Exposure compensation is adjusted in “stops”, usually in increments of stops of 1/3rd and ½, and 2/3rds, and 1 or more. 

A basic histogram on your cameras LCD is 5 stops “wide” , or from side to side.  Looking at this histogram example you can see its marked 0 – H along its bottom axis.  Most histograms are divided into 256 vertical segments numbered 0-255, so close together they look bunched up to form a sort of curve or “shape” showing where most of your scene was exposed.  If most of the vertical segments are bunched up to the left, the image will be underexposed as it is in this sample histogram.

 

A basic histogram on your cameras LCD is 5 stops “wide” , or from side to side.  Looking at this histogram example you can see its marked 0 – H along its bottom axis.  Most histograms are divided into 256 vertical segments numbered 0-255, so close together they look bunched up to form a sort of curve or “shape” showing where most of your scene was exposed.  If most of the vertical segments are bunched up to the left, the image will be underexposed as it is in this sample histogram.

 

This next example of a histogram shows the vertical segments bunched up to the right indicating overexposure.  If the segments touch the furthest right side then the image will be over exposed.

 

This next example of a histogram shows the vertical segments bunched up to the right indicating overexposure.  If the segments touch the furthest right side then the image will be over exposed.

 

This final example of a histogram shows the vertical segments all between the 0 – H (both sides) and as far to the right side as you can get without segments actually touching and/or going over the right side of the histogram.  This would be  “just right.

 

This final example of a histogram shows the vertical segments all between the 0 – H (both sides) and as far to the right side as you can get without segments actually touching and/or going over the right side of the histogram.  This would be  “just right.

 

In future columns you’ll see me attach histogram samples from time to time when they vary from the “norm” so you can get used to seeing what they look like for instance in night time scenes, sunsets, indoor with flash, etc.

The histogram is the single most important exposure indicator available to the digital photographer and learning to read and apply it properly is essential to producing good images.  Today’s automatic program modes will get you close, but through the use of your histogram and exposure compensation, you can fine tune the exposure to your individual scene, and produce much better results in many cases.