A histogram is a graph that depicts your image’s brightness when you review photos on the back of your camera or computer.
While this may seem like a basic topic to some of you, I have met a lot of photographers who don’t understand how to read this diagram.
Your shadows are on the left, your highlights are on the right and your midtones are in the middle. Scenes with a lot of dark tones will lean to the left, bright scenes will lean to the right and high contrast scenes will look like a valley. If your mountain hits the left you have pure blacks and if it hits the right you have pure whites, but if you properly expose an average scene, you with have a majestic mountain that sits right in the middle.
So, where should you be? If you want to capture more highlight detail, lean it to the left. If you want more shadow detail, lean it to the right. But don’t get crazy, because you may hit the sides and never recover those clipped details or you may introduce too much noise by underexposing your image too much. However, don’t stress out if you hit the sides because it may not be your fault. A black object in the shadows will naturally be pure black, and something super bright like the sun reflecting off a car windshield is not going to have detail. Not every screen is accurate, but a histogram doesn’t lie. So I would trust my histogram over an unfamiliar monitor. However, my Canon 5D Mark IV is fairly reliable. While I keep my screen brightness at 3 out of 7, the histogram’s always part of my process.