What is a Histogram and Why is it Important?
So remember when I said that the histogram represents the darker data on the right and the brighter data on the left? Well, there’s more to it than that.
The histogram actually represents levels of brightness on a scale from 0 to 255 for a total of 256 levels of brightness. Zero is pure black and 255 is pure white.
The X-axis (left to right) represents the brightness levels – Zero on the far left and 255 on the far right.
You can remember this by saying “left to right, black to white”.
But what about top to bottom? The Y-axis (up and down) represents the number of pixels. We don’t really have a standard scale on this though; but you can rest assured that the very bottom = zero pixels. And moving upward increases the number of pixels represented.
Let’s have a look, shall we?
Here are three histograms that represent a single luminance level. One white, one black, and one middle grey.
Notice the vertical white line in each histogram.
“Whoop-de-doo!” you may exclaim! That doesn’t help me much at all (or maybe it does – I don’t know). The next page should tie it all together.