>>3499414F-Stop, in short stop, are terms for the aperture. Increasing aperture sizes and decreasing f-numbers for "full stop" increments double the aperture area and thus double the exposure (i.e. EV=exposure value) or allow to halve the shutter speed at constant iso speed and constant EV.
Exposure value, short EV, is a term that corresponds to a change in exposure of a full stop, whether caused by aperture, ISO speed, shutter speed, or more sunlight or studio light. Most tend to just keep saying stop instead of EV.
The vertical lines in the histogram are usually whole aperture stops, i.e. 1 EV difference. This can be tested by halving the shutter speed at constant light and constant aperture thus darkening the image in 1 EV: The histogram should be moving left by the width of a section.
The histogram shows a dynamic range of 3 stops, the main part covers 2 stops. There are hardly any highlights to be enough to be accounted for in the histogram. The blues span 1EV, if you wanted it uniformly bright e.g. you could darken the bright parts in 1EV.
Also
>>3499231 but unironically. Alex Burke measures the exposure for setting his large format film camera and grad nd filters with a digital camera. He photographs or measures individual areas (sky, ground or the like in the spot or spot metering).
You can also do the same in image editing, do a cropping of an area to get a histogram of only that area and then compare it with other images or other areas to achieve consistent brightness editing or make sure a person is well exposed instead of the background.
