How to Correct Underexposed Photos in Photoshop CC 2015

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The underexposed image is shown in the upper left corner of the corrected image.
There are multiple approaches to dealing with an underexposed image. Here are four simple techniques.

It happens to the best of us.

We see something we think will make a great photo, whip out the digital camera and then discover, later, that great shot is seriously underexposed? If you have Photoshop there are a number of quick fixes available to you. Best of all you don’t have to be a certified Photoshop Wizard to turn out an acceptable result. In fact, the “Photoshop Wizards” master these techniques before earning their Photoshop Wizard robes.

For the average person looking to “fix” that amazing Family BBQ photo, it all comes down to nothing more than knowing where to look.

In this “How To…” we are going to use four different techniques to deal with an overexposed image. They are:

  • Correct exposure with the Exposure menu.
  • Use Brightness and Contrast
  • Understand how to read a Histogram in in Levels.
  • Use Adjustment Layers and Blend modes

Let’s get started.

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Technique 1: How To Use The Exposure Menu To Fix An Image

The exposure dialog box is shown over the corrected image and the sample point in the cloud is shown.
Exposure is to a quick fix but use the eyedroppers.

It was a glorious Autumn afternoon and standing at the top of the tower at Goosepimple Lake I just had to grab a photo of the glorious scene laid out before me, imagine my surprise to discover the photo was underexposed.

A possible solution is to use the Exposure menu found at Image>Adjustments> Exposure. Though the Dialog box may look a bit mysterious it actually covers off the three main areas of image correction: White Point, Black Point, Midtones, or Gamma. In this dialog box they are:

  • Exposure: Adjusts the highlights (White Point) and ignores everything else.
  • Offset: Adjusts the shadows (Black Point) and ignores everything else.
  • Gamma Correction: Adjusts the Midtones and ignores everything else.

What you don’t do is yank a slider. Instead, you use one of the eyedroppers—Black, Midtone, White—to “sample” a color. By that I mean the eyedropper will shift all of the highlights, Midtones, or shadows to the pixel you click on.

In this image, I selected the White eyedropper because, being underexposed, the image was dark and lacking highlights. I then clicked on the white cloud at the back of the treeline,

So how does the eyedropper work? When you click on a white pixel, in very general terms, the eyedropper looks out 5 pixels, finds the average white value of those pixels, and sets that as the base for whites in the image.

If you do use this technique, don’t look for a pure white pixel. Look for something, like that cloud, that is an “off white”.

Exposure is also available as an Adjustment Layer which lets you “tweak” the settings as opposed to the menu.

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Technique 2: How To Use The Brightness And Contrast Controls

The brightness/Contrast dialog box is shown over the corrected image and the Brightness and Contrast sliders are highlighted.
Brightness and Contrast work together. Don't increase one without decreasing the other and vice versa.

If an image is dark maybe it just needs to be brightened. This is sometimes the only thing to be done and, as you will see, that may indeed be a mistake. To get started I opened Image>Adjustments> Brightness/Contrast.

The dialog box that opens has two sliders: one for Brightness and the other for Contrast. There is also an Auto button. It should be avoided because the result is inconsistent. Instead, use your eyes to determine an acceptable result.

To brighten an image move the Brightness slider to the right. To darken it, move the slider in the other direction. In the case of this image, I moved the brightness slider to the right.

When you increase brightness, also take a look at Contrast. These two go together. If you increase the brightness, try reducing the contrast to bring out a little more detail in the image.

Brightness/Contrast is also available as an Adjustment Layer which lets you “tweak” the settings as opposed to the menu.

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Technique 3: How To Use Levels

The levels and Auto Color Correction Options dialog boxes are shown over the corrected image.
There are two approaches to using the Levels menu: Sliders, eyedroppers and the Auto Color Corection Options.

The third technique gets you down in the weeds with pixels and hands you a couple of ways of brightening up an image.

To start I pulled up the Levels menu. When the dialog box opens you will see a graph, called a Histogram, and the three eyedroppers.

A histogram shows you tonal distribution in the image. A great histogram resembles a bell curve.In the case of this image, the graph is shoved over to the left—the Blacks—and there seems to be nothing between the midtone slider in the middle and the White slider on the right. This is a classic example of an Underexposure histogram.

There are two ways of brightening the image.

The first is to drag the White slider to the left where there seems to be some tones on the histogram. As you move the white slider the midtone slider also moves to the left. So what is going on? Again, in very basic terms, you are telling Photoshop that all pixels between the white and midtones—126 to 255—now have a value of 255 which now lightens the affected pixels. The result is a brighter image.

The other method is to click the Options button in the Levels dialog box. This opens the Auto Color Correction Options dialog box. The four choices affect the image in different ways and, when you select an option, the histogram will also change. In this case, I selected Find Dark & Light Colors which really brought out the detail in the image.

Levels is also available as an Adjustment Layer which lets you “tweak” the settings as opposed to the menu. The Levels Adjustment layer does not contain the Color Correction Options.

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Technique 4: Use An Adjustment Layer And Blend Modes

Two Levels Adjustment Layers are shown. The top Adjustment layer shows the Sceen blend mode and reduced opacity.
Aleways use an Adjustment Layer to avoid serious color information loss in the image.

You may have noticed the previous three techniques all mentioned the use of an Adjustment Layer. Think of an Adjustment layer as handing you the ability to “tweak” your settings if things just don’t look right.

To this point in this “How To” everything you have done was essentially saved. There is no going back unless you are prepared to revert the image to its original state. The previous three techniques are regarded as “destructive” in that any change you make is permanent.

Remember that Histogram from the previous technique? A good histogram is a solid color. Apply one of the three techniques presented, reopen Levels and you will see a very different histogram. It looks like there are holes in it or as I like to say, “It looks like a picket fence.”

Those holes represent image information that was thrown out and never to be retrieved. Keep adjusting the image and the histogram will flat line even though the image may look fine. That is a classic case of destructive editing.

An Adjustment Layer is referred to as “Non Destructive” because the change is applied through a layer not directly to the image. If you don’t want the layer delete it and its effect on the underlying image is removed. Want to change a setting? Click the Adjustment layer and make the change. It is that simple.

In this case, I clicked the Adjustment layer button at the bottom of the layers panels and selected Levels from the resulting pop-up menu. A new Adjustment Layer appears above the Background layer. As well the Histogram appears in the Properties panel and I can adjust the White point by moving the slider or clicking on an off white pixel in the image to set the white point. In this case, I am going to do neither. Instead, I select the Screen Blend Mode and, when I release the mouse, the image brightens up and a lot of detail appears. What happened?

Blend Modes essentially apply some heavy duty math to the pixels in an image. With Screen, anything on the layer that's pure black will disappear from view. How that works, in very broad terms,  is all the “brightness” values in the image are averaged and the result is applied to all of the pixels in the image. Anything that's pure white will remain unchanged, and any shade of gray between pure black and pure white will become lighter.

For bonus points, you can improve the image even more.

Duplicate the Adjustment layer and instead of changing the Blend mode, reduce the Layer’s Opacity value. What this does is to “dial back” the brightness and bring up more detail in the image.