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Correcting Over/Under Exposure

The following technique can be used to attempt and salvage an over or under exposed image.  There are techniques one can use while scanning film/print or processing a Raw file to try and correct over/under exposure.  Correcting over/under exposure at the point of capture is the preferred method.  However, if this option is not available, the technique described here may help.

Note

Any part of the image over/under exposed to the point that detail is lost, will still have no detail once corrected.

 

Over Exposure

In this example, we will correct an overexposed image using the blending mode of an adjustment layer.  Figure 1 shows both the overexposed image and the corrected image.  The photograph was overexposed by 2.5 stops.

Overexposure Figure 1.  An overexposed image ...

Corrected image ... corrected by use of blending mode on an adjustment layer

 

 

Blending mode
Figure 2.  The blending mode change

To correct an overexposed image, try these steps.

  1. In the Layers panel, activate the layer containing the image by clicking on the layer.
  2. Create a Curves or Levels adjustment layer by clicking Layer > New Adjustment Layer.  Or, click the Create a New Fill or Adjustment Layer icon New adjustment layer icon at the bottom of the Layers panel.
  3. If the adjustment layer is not on top of the image layer in the Layers panel, click and drag the adjustment layer until it is.
  4. Make the adjustment layer the active layer.
  5. Change the adjustment layer's Blending Mode to Multiply, as shown in Figure 2.  Note no adjustment is actually made.  Only the blending mode of the adjustment layer is changed.
  6. If the exposure is now too dark, lower the Opacity of the adjustment layer. (More information about Blending Mode and Opacity can be found on the Layers Panel page.)
  7. If the exposure is still too light, repeat steps 2 through 5 to create a second adjustment layer.  If the exposure is still too light, the image may be hopelessly overexposed.

Under Exposure

In the next example, we will correct an underexposed image.  The underexposed and corrected images are shown in Figure 3.  The photograph was underexposed by 2.5 stops.

Underexposed image Figure 3.  An underexposed image ...

Corrected image ... corrected by use of blending mode on an adjustment layer

Blending mode
Figure 4.  The blending mode change

To correct an underexposed image, try these steps.

  1. In the Layers panel, activate the layer containing the image by clicking on the layer.
  2. Create a Curves or Levels adjustment layer by clicking Layer > New Adjustment Layer.  Or, click the Create a New Fill or Adjustment Layer icon New adjustment layer icon at the bottom of the Layers panel.
  3. If the adjustment layer is not on top of the image layer in the Layers panel, click and drag the adjustment layer until it is.
  4. Make the adjustment layer the active layer.
  5. Change the adjustment layer's Blending Mode to Screen, as shown in Figure 4.  Note no adjustment is actually made.  Only the blending mode of the adjustment layer is changed.
  6. If the exposure is now too light, lower the Opacity of the adjustment layer.
  7. If the exposure is still too dark, repeat steps 2 through 5 to create a second adjustment.  If the exposure is still too dark, the image may be hopelessly underexposed.

 

Tip

If only part of the image is over/under exposed, paint with black paint Black foreground in the adjustment layer mask to mask out all areas that do not need correction.  Remember, any part of the image over/under exposed to the point that detail is lost, will have no detail even when corrected

 

Caution

Use of this technique on a low resolution file can lead to posterization.  Posterization is shown as gaps in a histogram.  You can learn about histograms on the Histogram page.