Have you ever seen this weird graph show up on the back of your camera when you were checking out your photos?
That thing is a histogram, and according to Wikipedia “A histogram is a graphical representation of the distribution of numerical data.”
What that means is that a histogram is a graph, and that graph tells us information about our photos.
And in this series of videos we’re going to learn all about histograms, starting with what a histogram is and how to read it.
There are three different types of histogram, but all three types tell us about the the brightness values in the associated image.
Now reading a histogram is pretty simple.
The X axis of the graph represents all the possible brightness values in the image from 0% brightness, which would be pure black, to 100% brightness, which would be pure white.
However, the X axis doesn’t read from 0% to 100%. It actually reads from 0 to 255, where 0 represents no brightness, or pure black, and 255 represents full brightness, or pure white.
Now the Y-axis doesn’t start at 0 pixels at the bottom and end with however many pixels are in your image at the top.
Instead, the Y axis represents the proportion of pixels for the corresponding brightness value, and the top of the Y axis represents the largest single proportion of pixels in the image.
So a value that extends to the top of the Y axis in a histogram doesn’t always mean that that value is 100% of the image.
And when we look at the histogram, it tells us several things right away, but here’s the thing, it’s important to understand that looking at the individual values is not very useful.
We can look at a histogram and see that the pixels for any given value, occupy some percentage of the image, but that’s not very useful information.
What’s more useful is breaking the histogram into three regions, the shadows, mid tones and highlights.
When we look at the distribution of pixels by region, it immediately reveals several things about the image, without having to see the actual image.
Now histograms will tell you nothing about the subject of the image itself, which is pretty obvious, but it’s important to understand.
The histogram doesn’t tell you about how the pixels are arranged in the image, only about how bright or dark the pixels are and what proportion of the image they take up.
This is still really valuable information, because what we’ve got here is a graph that tells us about the exposure of our image,
When we take a photo, we capture light, and the histogram tells us about the amount of light captured, and how that light is distributed throughout the image, and this is really useful!
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Your camera is an amazing tool, but it’s no good to you if you don’t know how to use it!
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