How to read Histogram for Better Photography Exposure

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The histogram is an incredibly powerful tool that allows us to discover important aspects of the light during shooting, it is a great tool to better understand the correct photographic exposure. Learning how to read the histogram can take photography a step ahead and improve your photography exposure


Histogram Basics

The Histogram is a phisical representation of an image through levels. The Highlights and whites points are represented on the right side of the graph while the shadows and the blacks are represented on the left. In the middle part of the level there are the midtones while in the vertical axes is represented the number of pixels in a specific tone

Many cameras on the market are equipped with an histogram function that allows to view the relative graph for each image taken, in the form of levels. What the camera does is to create the histogram by converting the image to greyscale and divides it into 256 levels of brightness: starting from 0 up to 256, where 0 represents the pure blacks while 256 the pure whites. After analyzing the pixels of the image, the camera transform it into a chart


Understanding clipping Highlights and Shadows

Every time the graph moves too much on the right or on the left we talk about clipping highlights or clipping shadows, more pixel clipping on the sides of the charts and more information are being lost. Let’s see in details what does it mean

Clipping Highlights

Overexposed image

When we talk about clipping highlights we talk about loss of information on overexposed images, in this case the pixel portions where information are lost will be represented in the graph on the clipping part on the right

Clipping right graph

On camera raw there’s the possibility to put a tick to display the clipping warnings, in this case the highlights warning warn us for those areas where the pure white is, represented by the red color

Pure white warnings

To show the pure white areas in Camera Raw just click the top white arrow, in the image the area where I circled in red. Note than the areas in the sky, although they are extremely white and overexposed they cannot be considered pure white, is a subtle difference but only in the red part could be considered pure white points

Clipping Shadows

Underexposed image

Talking about the shadows the image below is underexposed so it’s more dark that how should it be, in this case the pixel portions where informations are losts are represented in the graph on the clipping part on the left

Clipping left graph

On camera raw also here there is the possibility to check for displaying the clipping warnings, in this case the shadows warnings are represented as the blue parts that corresponds as the pure black points

Pure blacks warnings

Same as the highlights also for the shadows to show the pure black areas in the image, just check the top of the chart, note that the areas on the rocks are extremely black and underexposed but we can consider the pure black parts only the blue areas selected in camera raw that are 100% blacks


So what’s the perfect Histogram?

The goal is to achieve the perfect histogram, to do that it depends of what are you photographing but in general, the perfect histogram is that has pixel spread throughout midtones and you don’t have lost of informations on clippings shadows or highlights

Below there’s a representation of just two different types of ideal histogram this to remembrance that’s not just 1 kind of ideal histogram but many types of it, depends on the scene and also other many factors that change from picture and picture. Essentially the loss of informations from shadows or highlights is something to avoid but also loosing too much midtones can “compromize” your perfect histogram


Why reading Histogram is Important?

After shooting a photo simply relying the review on the camera screen can be a mistake, because it does not give us a precise representation of how balanced the image is. It can happen that the camera LCD tries to represent the photo in a brighter and less precise way and once you open the shot into Photoshop you can find errors of loss of informations

As mentioned at the beginning of this article many cameras are equipped with the histogram tool, which after taking the photo allow you to view the representation in charts, in this way so it’s more easy and accurate to adjust the exposure

When shooting, using this tool is a great help to create more balanced photos. Personally I check the histogram on all the images I shot in order to keep under control the possible loss of information and not to lose dynamic range


My Method

As you know I make many of my shots using bracketing mode in order to capture every image with different exposures. Every time I take a photo I set the camera values to have a shot as precise and balanced as possible, I check the histogram to get the exposure more balanced as possible, then I activate the bracketing mode to achieve all the shots I need to capture the greatest number of dynamic range

I use the overexposed and underexposed shots only to realize my digital blending techniques and to selectively chose the necessary areas of interests for blending

Some exceptions:

Despite everything there are some styles of images that do not always require a perfect histogram which in this article I consider necessary to mentions, it is the case of all those images where a unperfect histogram is part of the intrinsic style of the photo

Without necessarily delving into each of these techniques I will just list them, maybe in the future if you are interested I will be able to create a guide on this topic. Exceptions are:

  • Low Key mages
  • High Key mages
  • High Contrast images
  • ETTR Technique

On this last technique I want to spend few words for a more detailed description: ETTR a photographic technique that consists in realizing the shots aiming towards a histogram to the right of the necessary one

The reasons behind this technique is that through this system it is possible to maintain a wider dynamic range and less information loss, in fact by successively lowering the exposure in the camera raw and reporting the exposure values in a balanced way the image final returns to being correctly exposed but with a greater possibility to manage the details within the shadows

Conclusions

So those was how to read the histogram for better photography exposure, as we see the histogram is an important tool for evaluating an image and a method for creating alternative photographic techniques. If you do not usually use it, I invite you to do it already from the next shots, I await your feedback on the results


Site Founder

Hi, my name is Giuseppe Sapori, a professional photographer and author of this website, created by yours truly to show my work and share with you the techniques I use. My expertise is in the field of Landscape Photography... (Read More)

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