If you are able to find the best possible exposure for every condition, shot or scene you should be able to take great pictures nearly every time that you click the camera shutter.
A histogram feature will present you with a representation of the total number of pixels that will be exposed in your camera shot. On the left side of the histogram graph, you can start to see the shadows and blacks whereas the right side of the histogram will let you predict the bright areas and highlights as well as the mid tones in a photograph.
How high the peaks reach will represent the total number of pixels in your photos that represent a particular tone. If 255 is white and zero is black, you can get an idea for roughly how bright your photo needs to be and how you should adjust your exposure accordingly.
How Histograms Help with Exposure
With tools like the histogram, it's easy to tell if an image is exposed well or not. If an image is exposed properly, it will reach from one edge of the graph to the other without going up drastically on either side. Professional shots generally show a histogram that only just touches the edges, does not spill out the sides and has a near-perfect arch through the center of the graph.
If you see gaps on either end of the histogram this means that you can be missing information from your photograph and that your exposure needs to be changed. Shifting your exposure just slightly can change the way that the graph appears and it can help you to cover a much broader range of tones in any shot that you are taking.
Spikes on the Sides of the Histogram
Left and Right side spikes on a histogram represent the loss of tone and detail that's being taken directly out of your photo. A clipped area is an area that's usually unrecoverable or unviewable in the image. This means that you won't even be able to edit this area to see it properly.
It's usually easiest to have some shadows or have a slightly darker image rather than attempt to overexpose a photo to highlight certain details. The spikes will definitely appear when it's impossible to keep your histogram graph within an acceptable range for the environment. When photographing in extreme conditions with deep shadows, this type of effect can occur.
Additional Reasons to Use Histograms
You can use a histogram for very important photos that you won't be able to capture again to make sure you get a great image the very first time. While many digital photographers rely on taking multiple images, this isn't always a possibility during very important moments. While burst shots can ensure you get multiple images in quick succession, it's important to use the histogram to get the right exposure and lighting conditions for perfect shots.
Pictures can look great on your camera screen but terrible on your PC; just because something might look like it's working on a small LCD screen, it doesn't mean that it is necessarily producing a great image quality. It can be tough to tell if you are using the right exposure on a digital camera screen. By using the histogram you can get a better picture so you can relax and focus on the shooting.