The Histogram is your Friend

The histogram is a graph of the light and dark areas in your photo

To determine if you have proper exposure on your digital images check your histogram on the back of your camera after every photo you take. It sounds like a lot of work to do this, but trust me, if your exposure is correct, you will have less “fixing” to do to your images afterward, so really, it’s a time saver.

The graph above illustrates the exposure of a photograph. The left side represents the dark areas, the shadows. The right side represents the bright areas, the highlights. The middle section represents the mid-tones.

After you take a picture you typically look at it on the back of your camera. You can’t really tell from the image playback screen if your photo is exposed properly, just like you can’t tell if the colour is correct. The brightness of those lcd screens varies a lot, and in the bright sun they can be impossible to see. So to really know if your photo is exposed properly, check your histogram. It will show you whether a photo is too dark, too light, or just right.

Interpreting the histogram

Hopefully the histogram of most images will be easy to interpret. If the graph doesn’t go all the way to the right side, it indicates underexposure. If it goes too far to the right, where it’s climbing the wall, then parts of your photo are overexposed, or too bright.

Sometimes you can have spikes on the highlight side of your histogram, but the rest of the histogram looks fine. This may indicate overexposure to the whole image, but it can also mean there is an area of shiny chrome, a glistening beach, or other bright area in your image. Even on an overcast day, the sky can be overexposed but the rest of the image can look great.

Examples

Have a look at the photograph below. I have an orange line going from the overexposed area in the sky to the part of the histogram is represents. I’ve also got a line to the mid-tones. As you can see, the exposure looks good, but the sky is blown out (over-exposed).

Photo and its histogram representing the overexposed sky

If I lower the exposure to make the histogram, and the sky look better (using exposure compensation +/-) then the overall exposure in the shot becomes too dark, like in the version below. I did pick up more detail in the background though, but I don’t think it looks as good overall.

Photo and its histogram representing the "fixed" overexposed sky

Your job is to determine what parts of the photo are most important and keep those exposed properly.

If you shoot jpg files, it is really important that your exposure is correct. If you overexpose your shot and lose highlight detail, you can never get it back. If your image is too dark, you can make it brighter in the editing process, but it won’t give you the best result.

For best results, shoot raw files

If you shoot raw files, you have exposure “insurance” and you can recover highlights, while retaining the mid tones and shadows.

The photograph below shows a quick correction in Adobe Camera Raw, that gives a compromise for this difficult exposure. Adobe Camera Raw is part of Photoshop and Photoshop Elements.

This was edited from the camera raw file and shows better exposure in the sky and foreground area

Want to learn more?

I teach an online course on how to shoot and edit raw files. Check it out today!

Comments

  1. David Mulligan says:

    You say that even an overcast sky can be overexposed. Other than the sun, and maybe the moon, an overcast sky or clouds are the brightest things up there. Overcast is significantly brighter than blue. I’ve learned to try to limit including the sky in my images if it is overcast. However even though I think I know how to use the histogram generally your article has me realizing that I need to experiment with including the overcast sky in my images.

    Do you have any advice for using the histogram to properly expose for snowy and ice rink type scenes? My son wears a very dark snowsuit and I am finding it difficult to get the exposure right to have detail in both the snow or ice and in his snowsuit. Part of why I am asking is that I used a picture and histogram to get the correct exposure for recording a video of my son’s skating lesson at an indoor community ice rink and the video was somewhat overexposed. Perhaps in this case I need to live with a little wall climbing.

    • You’ve just described one of the hardest shooting scenarios. Black on white.

      So, to keep the snow and ice bright white, I’d expose for the white. In other words you might have to open up a bit to keep the whites bright. Since you shoot raw, it’s fairly easy to correct for any stray overexposure. Plus sometimes a little overexposure in some areas is necessary to keep our subjects looking their best. And you can add fill light or brightness control to brighten the midtones, or go in and use localized adjustments on the dark snowsuit itself, in the RAW file if you’re using Photoshop or Lightroom, (or even Aperture).

      Shooting at indoor rinks is really hard at the best of times, and shooting video is doubly hard to correct for the scenario you’ve described. As your subject is moving all around, if you add exposure at the outset, your exposure might go all wonky on you. So I totally see how overexposure can occur.

      Shooting video is like shooting jpgs. You have to make exposure compromises and yes, you may indeed have to live with some wall climbing. If you do any video editing, you can usually correct for underexposure by bumping up the midtones in your scene. But just like jpgs, once you overexpose, that detail will be lost.

      Great question! Thanks for writing David.

      p.s. Buy your son a nice red or orange jacket when he outgrows this one, and you’re photos will come to life a bit more.