Using the histogram

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A histogram is a graph that represents the color division of an image over the color spectrum. The far left side represents 100% black color, while the far right side represents the 100% white. All other color tones are in-between. A histogram allows you to quickly check if the image is correctly exposed or if it is under or overexposed.


You can open the Histogram by clicking the histogram button in the far left Explorer bar.




That will open the histogram panel which by default is located at the right side of the application.You can drag the histogram our of the right dock area if you find a floating panel more convenient.




As you select a different thumbnail, this histogram will update for that selected thumbnail. When the histogram for a thumbnail is displayed than the histogram is calculated based on the thumbnail image or, if a preview is available, of the larger preview. Either way, this means that the histogram is indicative. The caption of the histogram panel also displays this identifier. As soon as you open the full image, the histogram will be updated using all pixels in the image. However, if you are using stored previews, than the histogram will be accurate.


The left side of the histogram contains a few configuration settings. These are:


More Settings

Click this button to open another panel with more settings.




This extra panel allows you to select which color channels should be contained in the histogram. Options are: red, green, blue, and RGB (combined to gray tone)


You can also configure if the histogram should be displayed as a bar diagram (filled area) or as a line.


After changing the settings, you can click the settings button again to close the left panel.


3D setting

Click this button to switch the histogram in a 3D view.


Sometimes it is hard to determine where the histogram peaks. This is mainly the case when there is a large peak at the end or at the beginning of the histogram. This is why IDimager includes a 3D mode for the histogram, the 3D mode can be activated by clicking the 3D button at the left of the histogram.




As you can see; in the 3D histogram is much easier to see where peaks are. IDimager is the only tool we know of that allows a 3D histogram display.


Clipping setting

Often a histogram contains a one or more large peaks and then the rest of the histogram become hard to interpret because it is all at the lower end of the diagram. That is why you have a clipping setting. With clipping you can determine if peaks should be clipped off the diagram so that the rest of the diagram pulls up.


Clipping options are:



None; No clipping is applied

Minimal; The histogram is clipped at 50% above the average peak size

Common; The histogram is clipped at 20% above the average peak size

Average; The histogram is clipped at 10% above the average peak size

Maximal; The histogram is clipped at the average peak size


Print histogram

Output the histogram to a printer





A sample histogram; displays RGB+Red+Green+Blue in a bar style


A sample histogram; displays Red+Green+Blue in a line style


The next chapter offers some information on how to interpret a histogram.