Staring at a perfectly constructed histogram is like listening to an opera singer hit and hold a perfect note. But in trying to get that histogram to look like you're being told it should, you could be ruining potentially great images.
Ah, the histogram, eh? That weird-looking mathematical graph thing in the top right of your Photoshop or Lightroom screen that gives you scientific calculations of your blacks, shadows, midtones, highlights, and whites. At some point on our photographic journeys, we've all been told to pay more attention to the histograms on both our cameras and editing software, and rightly so. Sometimes, your eyes, or your screen, or the monitor you're using can play sneaky little tricks on you and tell you things that just aren't true. But science and binary numbers just don't lie. Indeed, the histogram is an incredibly helpful tool that should be part of everyone's repertoire.
However, it can also be problematic when we pay too much attention to it and start allowing it to dictate terms to us. What do I mean? Well, I'm sure we've all come across videos, or instructional guides, or graphics in books that tell us that the ideal histogram is to have a nice spread from left to right with most of the colors falling in the range between shadows, midtones, and highlights, and falling away at the extreme ends of the blacks and the whites — kind of like a nicely shaped mountain, if you will, as you can see in the image below.
This is a lovely histogram indeed, and if I looked at this alone in trying to determine if my exposure was correct, I'd be a pretty happy man. But alas, sometimes, this can lead us down a painful journey of ruinous editing and volcanic frustration. Let me give you an example, so you can see exactly what I'm getting at.
This is a photo of my wife on a recent trip to a local shrine for my eldest daughter's third birthday. She looks radiantly gorgeous to me, but gasp, horror, shock, look at that histogram. All stacked up over on the left side like that, it makes me think that my image must be underexposed and far too dark. I mean, if we compare this histogram with the "ideal" histogram above it, this thing needs a lot of work to push those darks further to the right. And this is where we get into problems.
For the sake of demonstration, I decided I'd base my final image on the pursuit of the perfect histogram alone. And I hit the jackpot. Check out what I got below.
Isn't that histogram just divine? It's the prettiest thing I ever did see. Unfortunately, however, I've turned my wife into a pasty, brunette HDR cartoon from The Walking Dead. No matter, though, because my histogram is bang on. In all seriousness, you can see that this is a problem. Paying too much attention to the histogram can take wonderfully exposed images and turn them into fodder for online hate groups. The original image that we thought was underexposed because the histogram was pushed over to the left was actually perfectly exposed and needed no changing whatsoever. Here's another example below.
If we look at the histogram in isolation, we might think, again, that this image is underexposed. Like the first one, we can see the histogram pushed way over to the left with seemingly far too many blacks and shadows compared with highlights and whites. If we based our judgment on this histogram, then we might start editing and end up with another HDR cartoon. Surely I couldn't do that to my two daughters, too? Maybe I could some days.
So, what's the solution? How do we look at images that seem to be underexposed like these two here and determine whether or not they're actually exposed correctly or not? It's a very simple fix. In the first image of my wife, she is obviously the subject and the focal point of the image. She is looking at some wooden blocks (called "ema" in Japanese) with wishes and dreams written on them, but they are secondary points of focus. There is only one real subject in this image: my wife. So, all we need to do is determine whether my wife is correctly exposed or not. To do that, all you need to do is select the Quick Selection Tool in Photoshop, then click the Select Subject button, as in the image below. It's that simple.
Once you do that, Photoshop will work its magic and select your subject for you. You'll see that it's done its job when all the marching ants appear around your subject. When that happens, you then just need to look at your new histogram. Most likely, it's looking a lot better and isn't appearing all crushed over on the left side, like we saw originally with this image. Check out the image below to see what I mean.
You can see the marching ants around my wife, but more importantly you can see that my histogram now looks a lot better than it did before. Why? Because now Photoshop is showing me a histogram for my wife only. It's not taking into account any other part of the image and is focusing only on what is inside the marching ants selection. In the earlier image, when the histogram was showing us a seemingly underexposed image, it was taking into account the entire frame. Well, that's all well and good in some instances, but in cases like this, and particularly in portraiture, we don't really need the histogram for the whole image. We just need it for our subject. Let's have a look at my other image to reinforce my point.
Again, I just selected the Quick Selection Tool in Photoshop and clicked Select Subject. After Photoshop weaved its magic and threw an ant colony over my family, we can see a histogram that looks much better, because it's not worrying about the other elements in the frame, including my subtle, little vignette. It's only focusing on the subject, and in doing so, it's displaying a far more palatable histogram and rendering pointless my need to zap the living hell out of my family with all sorts of weird, funky editing work.
Histograms are important. They give us a great representation of what's going on in our frame, particularly with regards to exposure. But sometimes, they can be deceiving, especially when you're shooting portraits. So, if you have a histogram on an image that is troubling you, then simply select your subject only, and you might have your concerns allayed somewhat.
I'd love to hear your thoughts in the comments below.