The four images below were all taken hand-held with some of the exif data captured on the screen print. The images were taken indoors with (so called) consistent lighting from my LED spot lights in my living room. I shot the images in quick succession in the P mode of my Nikon D750. The thought process behind the speed in which the images were taken, was to illustrate how the histogram has changed. Boris, my trusty mate, was hardly moving as he lay snoozing after his morning walk. The only real change is his awareness of me taking his photo. His eyes have opened and then started to close, once he reaslised what I was doing.
I have screen printed the images from my Lightroom Library and included the Histogram as part of the screen shot. Eventhough the images were taken within 2 seconds of each other, you can see a clear difference in the way the histogram shows the distribution of the toned, especially relating to the darker pixels of the image on the left hand side of the histogram. Compare and contrast the first image to the last one to see a marked difference. The framing is the same but the distribution of the tones the histogram is different.
A map that is used to represent the distribution of tones in an image. The horizontal axis goes from darkest to lightest whilst the vertical axis shows the number of pixels in that specific range.