Histogram Definition

What is histogram

A histogram in Photography is a graphical representation of your photography and light level that helps you evaluate exposure. Before digital photography, we did not know whether we received good exposure or not. Today it is visible on the camera display.

The image preview your camera displays is good for checkup composition. The brightness and contrast of the image vary both with the LCD's setting and with the changing ambient light. The picture you see is a JPEG and it does not display the full range of tones captured. The best way to determine exposure is to use the histogram.

How to use a histogram 

If you know how to use a histogram, this tool will become indispensable to you during photography. 

There are two types of histogram on the camera. Luminosity histograms and RGB  histogram. Both tools must be used for exposure analysis. 

Luminosity Histogram

On the Luminosity histogram, blacks tone are represented on the left side of the graph and the pixels close to the left edge of the histogram are equal to 0% brightness. Whites are represented on the right side. Pixels close to the right edge of the histogram are equal 100% bright. Between these are you have the mid-tones, which are neither completely black or white. The vertical axis of the  Luminosity Histogram symbolizes the number of pixels that are in that tone.

RGB Histogram

The RGB  histogram (red, green, blue) shows the color you captured. The camera uses this color information to interpolate the actual color for that location on the sensor.

It also uses the color brightness to assemble individual red, green and blue histograms. The RGB histogram, display as three separate graphs or all three colors overlaid on a single graph. 

How to read the Histogram

You should be able to read the histogram for proper use. A histogram is a visual hint of a photographer.

The blacks are on the left, whites are on the right and mid-tones are between them. 

Histogram Chart

Let’s look at the histogram chart.

On the chart shows luminosity and RGB histograms. You see darks, shadows, midtones, highlights and white pixels on a graph. This is a visual chart of the number of pixels in your photo.

There are three histograms too. This is the RGB histogram. These graphs show the red, green, and blue pixels of your photo.

As a general rule, dark pixels are located to the left, and light to the right.

Free download Histogram Chart PDF

Reading a histogram

Reading a histogram allows you to accurately analyze the exposure during photography. On the exposure histogram chart, I show five typical histograms. 

You should avoid overexposure and underexposure. Underexposure is a mistake. Most likely is a night time pic. This photo will be difficult to fix. Take a longer shutter speed. 

Like underexposure, you should avoid overexposure too. The information about highlights and white is lost. It is a broken photo. 

Free download How to Read Histogram Chart PDF

Ideal Histogram

An ideal Histogram in photography is a graphical representation of the tonal values of an image of a certain brightness found in your photo, ranging from black (more than 0%) to white (less than 100%).

Histogram clipping.

Histogram clipping is the 'touching' one of the edges of a graph.

1. Highlights clipping occurs if the graph is touching the right side of the histogram. White details are absolutely absent in the image.
2. Shadow clipping occurs if the graph is touching the left side of the histogram. Black details are absolutely absent in the image.
3. Color clipping similar to highlights and shadow clippings. Details one of colors are absent.

Please check out some of my previously published free tutorials in my archives.

• Exposure 
• Understanding ISO 
• The Aperture in Landscape photography
• Exposure triangle 
• The Depth of Field 
• White Balance is part of the Exposition 
• Exposure Triangle cheat sheet
• Shutter speed chart
• 3 Easy Steps to Fix White Balance in Photoshop
• F-Stop Chart

Anyone have any tips to add? Please share in the comments!