Level 2 Plus

Lesson 11

Levels
Exposure Correction

This lesson will show you one method of correcting exposure. An alternative method will be covered in Lesson #12.

Introduction

In this lesson, we will show you a method of correcting images that are either overexposed or underexposed.  You will use the “Levels” function to accomplish this.

In “Levels”, we will use the “Shadows” slider and the “Highlight” slider to reclaim the full dynamic range.

In “Levels”, we will use the “Midtone” slider to fine-tune the adjustments.

This is the image of the flower that we dealt with in the last lesson.

This image is properly exposed.

In this lesson, we will consider an overexposed and an underexposed image of this flower.

We will use “Levels” to attempt to bring these back to the correct exposure.

From the Main menu, we clicked on:

[ Edit ]

From the drop down menu, we clicked on:

[ Go to Standard Edit ]

In the “Standard Edit Screen”, we have moved to the Main menu & clicked on:

[ Enhance ]

Then we clicked on:

[ Adjust Lighting ]

Finally we clicked on:

[ Levels ]

Digital cameras don’t always manage to use the full extent of the tonal range available to them.

If we move the “Left Black Point“ slider to meet the left side of the graph, we can reclaim unavailable shadow information.

If we move the “Right White Point” slider to meet the right side of the graph, we can reclaim unavailable highlight information.

1.      Reclaim shadow area – if the left edge of the curve doesn’t come to the “Black Point” – move the left slider to meet the right side of the graph, as shown.

2.      Reclaim highlight area – if the right edge of the curve doesn’t come to the “White Point” – move the right slider to meet the left side of the graph, as shown.

3.      Move the Centre Midtone slider to taste – by watching changes in the image itself.

This pane shows the sliders in their final positions.

We will now illustrate these principles with actual examples.

The image in the far left pane is underexposed.

The Image in the middle pane is correctly exposed.

The image in the far right pane is overexposed.

This image is correctly exposed.

The “Levels” pane bears this out by showing a graph with a good amount of information in the mid-tones and no loss of shadow or highlight information.

No Levels repair is required.

This image is underexposed.

The Levels pane bears this out by showing a graph with a large amount of information in the dark tones and little information in the mid-tones and highlights.

As well, there is loss of highlight detail since the right side of the graph does not meet the right highlight slider

Levels repair is required.

1.      Move the “Right Highlight” slider to meet the right side of the graph in order to reclaim lost highlights.

2.      Move the “Midtone” slider to the left so that more of the exposure is in the mid-tones.  Look at the image while you move the slider to taste.

This comparison shows the before and after “Levels” screens.

You can see that the underexposure has been corrected and the new “Levels” screen shows a better distribution of tonal values.

This comparison shows the before and after images.

You can see that the underexposure has been corrected and the after image reflects a fairly normal looking exposure.

This image is over exposed.

The “Levels” pane bears this out by showing a graph with a large amount of information in the light tones and little information in the mid-tones and shadows.

As well, there is loss of shadow detail since the left side of the graph does not meet the left shadow slider.

Levels repair is required.

1.      Move the “Left Shadow” slider to meet the left side of the graph in order to reclaim lost shadows.

2.      Move the “Midtone” slider to the right so that more of the exposure is in the mid-tone. Look at the image while you move the slider to taste.

This comparison shows the before and after “Levels” screens.

You can see that the overexposure has been corrected and the new “Levels” screen shows a better distribution of tonal values.

This comparison shows the before and after images.

You can see that the overexposure has been corrected and the after image reflects a fairly normal looking exposure.

The correction of overexposure was not as successful as the correction of underexposure. “Levels” isn’t perfect. It is always better to take a properly exposed image with your camera and leave less for “Levels” to do.

The left image is the original properly exposed image. It is the best image.

The middle image is the corrected underexposed image. It is the second best image.

The right image is the corrected overexposed image. It is the least acceptable image.

Both corrected images are better than the uncorrected images.

In this example there has been a loss of dynamic tonal range with a loss of both highlight and shadow detail.

The image appears very flat with no highlights or shadow information.

Here we have moved the left and right sliders in to meet the edges of the graph.

Then we moved the middle slider to taste.

In this example the dynamic tonal range has been restored, reclaiming both highlight and shadow detail.

The image appears very vibrant with good highlights and shadows.

Summary

In this lesson, we covered a method of correcting images that are either overexposed or underexposed.  We used the “Levels” function to accomplish this.

In “Levels”, we used the “Shadows” slider and the “Highlight” slider to reclaim the full dynamic range.

In “Levels”, we used the “Midtone” slider to fine-tune the adjustments.