Modern cameras are so technical and there are so many things to consider when you take photographs that it is almost forgivable if you do not give your histogram that much attention. But these little hills on the side of your screen can be incredibly helpful in getting the right exposure for your photo.
Let's take a look:
I took the photo above on normal exposure. In other words I took a center weighed light reading through the camera and made no exposure compensation.
If you look at the histogram from the picture above you can see that there are peaks in the middle and that it does not touch on the sides of the frame. (Disclaimer: the histograms I use here are from my editing software, but it serves the same purpose)
And the effect is that there is beautiful detail and colour on the flowers.
The next picture I took I deliberately over exposed the image.
This is the effect on the histogram. Notice the graph pushing all the way up against the wall on the right hand side? This is not good.
The implication of this is that a part of the picture has gone pure white and lost all it's detail.
Have look at the close up:
Now let's see what happens if I under expose the picture:
This first thing you might notice is that all the lighter colours have gone all muddy. It is not pretty, but perhaps it can still be saved to a degree in editing.
But when you look this picture's histogram, you can see that there may be an even bigger problem: The graph is pushing up against the left had side this time. Again this is not good.
So what does all of this mean?
It means that the information that you've lost is gone for ever. If it is not too bad, perhaps you can retrieve some of it if you shot RAW files as these have a better dynamic range than Jpegs, but you'll always have the risk that some information is lost forever.
The solution?
Take a test shot before you do your shoot. If the graph touches on either side of your histogram you know you are on risky ground. Make adjustments to your exposure and test it again. Once you have an even balance and the graph does not touch on either side, you're good to go and you can shoot with confidence.
The place between the two sides where your graph will stand, is determined by the tone of your subject. Lighter tones will lean toward the right and darker tones toward the left. (Just make sure it doesn't touch the sides!)
Remember that every time your light conditions change, you'll have to do a test again.
Because histograms are based on science, it actually is much more accurate in determining if your exposure is correct than by looking on the screen at the back of your camera. Play around with it and become good friends with your histogram. Those little hills will serve you well. And let me know how it worked for you. Until next time. Cheers
Ron
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