What is that little graph on the back of your camera and in your editing program and do you even need to know?

Understanding the Histogram

 

If you’re like me, I didn’t really know what the histogram was for, and didn’t really care what the histogram was.  It sounded complicated and I am not a fan of complicated!  I look at the back of my camera, it looks good, done.  And most of the time that is exactly all you need, “but”,  the Histogram holds information about your exposure you may not see on that little LCD screen that could really make or break a photo.  It is true, our cameras are remarkable at recovering from our poor exposures, but if we just knew what that little graph was telling us we might just save ourselves some grief, but first, lets “un-complicate” it .

 

The histogram is simply a visual, graphical representation of the light as it is recorded on our sensor.  Your camera doesn’t know if you just took a picture of Aunt Annie or Aunt Annie’s Alligator.  All it knows is it recorded light of different values (lightness and darkness) and different colours.  The graph you see is showing you what it recorded and from it you can tell if you will have enough information in your file for a reasonably  good or even great exposure.  Most of the time we can see the image we took on the  back of our camera and tell it’s pretty good, (or not).  Some of us  have another feature we can turn  on and see blinking black areas if we over exposed it.  Most of the time this is enough.  If you have Lightroom, you can click the little triangle at the top corners of the histogram and see if you have lost shadow detail or lost highlight  detail.  It really does come in handy  now and again.

So lets look at 3 images in Lightroom (it can be any software that shows us a histogram) and see what we can learn by quick observation.

 

In this first image, the scene is quite dark and it has very little brightness.  It does have lots of small light sources.  Notice how the “weight” of the graph is toward the left.  This means most of the exposure is dark.

Sunset down on the Docks

In our second image, the scene is quite light with areas of white with good brightness.  There are some dark areas but not many.  Notice how the weight of the graph is to the right.  This means the image is mostly light

Brianna in White

And in our third image, it is low in contrast and neither very dark or very light.  Notice how the weight of the graph is mostly toward the middle.

HistogramTutorials002-2

So you can see in these examples how the histogram is seeing and representing what the camera recorded.

If your graph leaves the left side of your histogram, you have pure black areas, known as “blocked up” shadows . It is underexposed and created pure black with little or no recoverable detail in the dark shadows and you may not want that.

Sunset down on the Docks

If your graph leaves the right of your histogram, you have pure white areas, known as “blown out highlights”.  It is overexposed and created pure white. There is little or no recoverable detail in the highlights and you may not want that.

  Brianna in White

There is much more to uncover about the histogram and it’s usefulness, but for a start, this is a good foundation.  For many, It’s all you will ever need to know.