BEGINNERS GUIDE TO READING A HISTOGRAM
The histogram. A little graph that I’m sure you have seen or heard of before. You will also see it appearing at the top right hand side of both Lightroom and Photoshop. But what is it? How can you read it? And how will it help improve your landscape photography? Sit tight, grab a cup of tea and I’ll tell you.
Right, you will see a histogram with most editing suites like Lightroom, Photoshop and most modern cameras will have one built in that you can view on the back of your LCD screen.
How Can I Read The Histogram?
The histogram is a digital representation of the tonal range in your image. Basically, the histogram records all the data from your image and shows you what is shadows, highlights and everything in between. Typically it will look something like the diagram below.
If you look from the bottom of the graph, from left to right, you will see blacks, shadows, midtones, highlights and whites. So, if all of the information is to the left hand side of the histogram your imagine would be dark or in some cases underexposed. If all of the information was to the right, then your image would be overexposed. This is why it is vital to keep an eye on your histogram.
Clipping
What does clipping mean? If any portion of the graph is touching or past either side, this is known as clipping. Clipping means that you are losing detail within the image. Highlight clipping means their are areas that are completely white and void of detail. Shadow clipping means their are areas that are completely black and void of any detail. Just to recap, that if the right hand side of the histogram is touching the edge or past the side of it, that means the highlights are clipping (too bright). If it is the left had side, its shadows that are clipping (too dark).
Here are 2 examples of highlight and shadow clipping. The left histogram is shadows clipping and the right is highlight clipping.
On some cameras, you may also get a warning that you have clipped highlights in the form of a “blinkie” below.
How to fix highlight or shadows clipping in camera?
So, you are set-up and the scene is in front of you and you have noticed that either your highlights or shadows are clipping. You can adjust and change this by either increasing your ISO, widening your aperture or lengthening your shutter speed. Another thing you could do to help is dialling in a positive image compensation value (+0.3 or +0.7, for example); to save highlight detail, make images darker by dialling negative exposure compensation value (-0.3 or -0.7, for example). Exposure compensation is usually set using “+/-” button on your camera.
Remember, this is just a very quick guide on how to read a histogram. There are examples when your image will clip, like when you’re shooting directly into the sun. You may intentionally want your image bright or dark too. I tend to use the histogram as a guide to how I want the final image to look. My advise to you would be, always shoot to the right. What does that mean? It means try and keep you histogram more weighted to the right if you can. It is easier to recover detail in the highlights then it is in the shadows.
I hope this very brief explanation on reading histograms helps? If you have any questions, please feel free to contact me and I’ll be more than happy to explain more.
Happy Shooting
Tim Monaghan
