At first sight the histogram can look like a very complicated and daunting technical graph. For this reason alone a lot of photographers avoid using this very useful tool.
In reality the histogram is not nearly as complicated as it looks and is actually one of the most useful tools at your disposal. In fact if you want to get the correct exposure almost every time then you need to be using the histogram.
Basically the histogram is a graph which illustrates the tonal range in an image. The scale runs from 0 on the left to 255 on the right. On the left you have black, in the centre is 18% grey and pure white to the right.
The height of the graph at any point represents the number of pixels in your image with that level of brightness. The overall shape of the graph gives you an indication of the tonal range of the image.
Why Use the Histogram?
So why use the histogram? After all when you take a photograph the image instantly appears on the camera’s screen. You can see with the naked eye whether it is correctly exposed, Right?
Well yes and no. You see the quality of the screen is never going to be good enough for you to see the full tonal range of an image. For this reason it can be difficult to judge whether part of the image is slightly too dark or too bright.
Using the histogram enables you to see at a glance whether your image is correctly exposed or not. Enabling you to achieve the best tonal range possible.
Once you become familiar with using the histogram you will be able to tell instantly if the exposure is correct. This means you will be able to compensate for this and your next shot will be perfectly exposed.
It’s not just exposure the histogram helps with, it’s also invaluable for getting the contrast and the tonal range correct. In doing so you will end up with a more satisfying final image. It also enables you to take extra care when you are dealing with difficult circumstances such as subjects with a high dynamic range.
Using the histogram also ensures that you get the best from your cameras sensor. Especially when shooting low contrast subjects. If you want to get the best results when shooting tricky scenes you need to know the brightness range you are dealing with, the histogram helps you to do this.
How to use the Histogram
Once you know what you are looking for the histogram really is a very simple tool to use. You should be aiming to have your histogram reach both edges of the graph. If there is a space to the left your image is probably overexposed with not enough detail in the highlights. If there is space to the right your image is most likely underexposed with not enough detail in the shadows.
Don’t panic if your histogram is more to one side or another. This is not wrong it just means that your subject is predominantly dark or light.
Of course there are exceptions. You may want to shoot a high key subject or a very dark moody portrait in which case the histogram will not read as a correctly exposed image.
Summery
By using the Histogram on your camera you will find it easier and faster to get the correct exposure for even the most challenging of scenes. Although you can adjust the levels in post processing it is better to get everything right when taking the photograph in the first place. Remember if you are shooting in jpeg format any adjustments you make in post processing will be detrimental to the quality of the final image. For this reason alone its worth taking time to get to know the histogram tool.
