Histograms, Easy and Important to Understand

© Article and photography by William Manning

That strange looking graph that accompanies every picture you take is called a histogram, you probably already knew that or at least heard the term. There has been much written about the histogram and for good reason. Back in the days of transparency films we workshop leaders spent an enormous amount of time explaining exposures to the point it became confusing for many photographers. Today we spend very little time explaining exposures although correct exposure is equally important with digital as it was with film. Some photographers simply decide they’ll correct the exposure problem in the computer, some figure if the photo looks good on the LCD screen its good enough but the perfectionist uses the histogram to get it right. Histograms may not seem important if all you’re wanting is to show your photos on an iPhone or Facebook, but if you want your photos to look great everywhere else then attention to this important detail plays a vital role in your work. Histograms are important and shares valuable information to the discerning photographer. Today there is no reason for leaving a photo shoot hoping you got the exposure right.

There are different ways to explain a histogram, a detailed explanation, which most photographers don’t care about and an easy all you need to know explanation. I’m going to take the second and try to give a straight forward answer that will improve your photography instantly.

What is a Histogram

A histogram is quite simply a graphical representation and visual distribution of data, in the case of photography the data is exposure information.

Histogram chart

The histogram can be found in several different places, the most common is the LCD screen on the back of the camera, most cameras require you set a custom function to show the histogram, others a click of a button, some cameras show the histogram on the top LCD where shutter speeds and f stops are shown, others are superimposed over the photo. Check your camera manual if you’re not sure. The other place most people see a histogram is in a post processing program such as Adobe Photoshop, Lightroom or Bridge.

When you see a professional photographer looking at the back of their camera while shooting they are checking their histograms, most of them I hope. This is what I do, I don’t need to see the photo, I’m well aware of what I just shot, I’m much more interested in seeing if I got the exposure and if I need to make adjustments. The best place to make exposure corrections is in the field not the computer. There are good reasons for this, first, blown out highlights cannot be retrieved in the computer, if they are not recorded then they are lost. The second reason, underexposed shadows or dark tones carry noise and are difficult to fix and when they are fixed much of the time the image is degraded to some degree (often a soft looking photo). A third reason, when you can’t get the exposure to fall where it needs to be you have options, such as multiple exposures for HDR.

Note: noise is visual distortion or splotches of discoloration typically found in dark areas of a photograph.

I know some photographers who are reading this will say their photos look just fine on their laptop, Facebook page, website, iPad, iPhone, etc… This may be true but I take pride in a well crafted image and hope others might be interested in my work and purchase it for commercial purposes or a nice wall print. There’s nothing more embarrassing than handing over a print or a digital file and the client telling me the picture looks nothing like the one they saw on the computer. Be a perfectionist and get it right.

Easy Steps to Getting It Right

The above chart pretty much says it all. The right hand side of the graph allows you to see where your highlights

example #2

example #2

fall, if they go beyond the window as shown in example #2 then your bright areas or highlights are over exposed, you can correct this by closing down your aperture or shutter speed, letting less light into the camera. When you do this it will move the entire graph and your shadows or darker tones will become darker, it is quite possible when you get all of your highlights to fall within the graph window your shadows will fall outside the graph window on the left side creating another problem.

example #3

example #3

When your histogram falls outside the graph window as in example #3 you simply do the opposite of the last example, open your aperture or shutter speed letting more light in. The same holds true here as mentioned above, when the correction is applied the highlights may fall outside the graph window, this is certainly going to hold true with the histogram in example #3.

When you have a situation where you cannot get the histogram to fall within the graph window on both the shadow and highlight side you have to make s decision, either compromise by determining what is more important the highlights or shadows and allowing that area to fall within the graph window and letting the other fall outside or create an HDR. If my graph is grossly falling outside the window on one side I will do a HDR. If one side falls within the window and the other just barely exceeds the window I will let it go and not worry about it unless it is an important detail. I will discuss HDR in another article.

At the time of photographing on location you may be thinking the photo won’t be seen beyond your Facebook page or your iPad, but you never know the importance or potential of a photo until sometime down the road. Get it right in camera the first time and most likely the only opportunity and avoid disappointment down the road. If you want a more detailed or scientific explanation of histograms there are plenty of great explanations on the web, but for the most part this is all you need to know to capture a fundamentally strong image.

© Article and photography by William Manning

William is the founder of Photovian and is a travel and architectural photographer. To see more work of William visit his business website at www.williammanning.com.