How to read histograms

When you are new to photography, everything can look scary. You are trying to master the manual mode and there are so many things to consider, to check and to set. You may think a histogram is very complicated and talk yourself out of paying attention to it, let alone to learn it.

But in fact, the histogram is a very helpful tool and is not complicated at all. Once you know what it shows and how to read it, it will become one of your most helpful friends in photography.

What is a histogram?

Histogram is a graph explaining your exposure, the amount of light that reaches your camera sensor. It will represent where the data is captured and what part of it is in the shadows, the mid-tones and in the highlights.

 

How do histograms work?

A luminosity histogram takes a grey scale version of your image and divides it up int 256 levels of brightness, where 0 is pure black and 255 is pure white.

The horizontal axis moves from pure black on the left side of the histogram, over shadows, mid-tones to highlights, and whites on the right side. The vertical axis represents the intensity of each tone, where peaks mean high frequency. You don’t need to concern too much about the height of the peaks, the horizontal portion is more important to judge your exposure. Most digital cameras and photo editing softwares have both a luminosity and a colour histogram.

Right-side peak histograms

If your histogram is heavily weighted on the right side, it means there’s a lot of highlights detail in the image, or your photo might be overexposed.

 

Left-side peak histograms

If you have high peaks on the left side of your histogram, it means that the blacks are clipped and you are losing detail in the shadows. In other words, the photo is underexposed.

Middle stacked histograms

If most of your pixels form a mountain in the middle of your histogram, it means it’s heavy on mid-tones, and your image may lack contrast.

Spikes on both sides histograms

Spikes on both sides on the histogram mean that the largest tones are in the highlights and in the shadows, so the photo is high in contrast.

 

 

Is there a correct histogram shape?

Histograms vary from photo to photo, and there is correct or incorrect histogram.

However, your histogram should always reflect the actual tonal values of your scene, so you have to make sure what you see on your camera’s LCD screen is reasonable. For example, if you are taking a picture that is meant to be bright and airy, or the object is white in a white background, it’s perfectly normal to get a right-weighted histogram.

What is clipping?

If you see a spike on either the left or right side of the histogram, it means you captured pure black or pure white information with no detail. Pure black and pure white can’t be recovered in post-processing.

Clipped areas are pixels that are sitting at each end of the histogram. The spikes mean data loss in those areas. Pure black and white tones can’t be recovered, so it’s worth checking the histogram whilst you are shooting to avoid it. If you are shooting indoors and tethered and use a software like CaptureOne, then you can immediately see the clipped (burnt) areas.

In Lighroom the triangle in the top left corner will turn black if your blacks are clipped, and the triangle on the right-hand side will light up white if the whites are clipped. If you see a different coloured triangle light up, it shows the individual colour channel.