Image Processing Histogram

I have two images : a hazy one and a haze free version

https://preview.redd.it/pm07gay02lwa1.png?width=716&format=png&auto=webp&v=enabled&s=a31ba7cc1ef5d01f4ffb7deda70ebb50ba74a33b

I am getting the following histograms for the images

https://preview.redd.it/lykcy7p72lwa1.png?width=1374&format=png&auto=webp&v=enabled&s=7666063ead2acef0a309df4b8db41d9222a63eb4

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Why the hazy image histograms have gaps in the plot ? Also is there any other key difference in the two histograms of hazy and unhazy image that I am missing ?

computervision difference free histograms image image processing images plot processing