Nondestructive Editing In Photoshop -- Part I

Article and Photography by Ron Bigelow

Photoshop CS4 Used in this Tutorial

The ability to digitally edit photographic images is one of the biggest advantages of digital photography. Edits can now be made in seconds or minutes that would have taken large amounts of time and effort in a wet darkroom. However, from a quality perspective, not all digital editing techniques are equal. Some types of edits produce better quality images that other edits.

All types of image edits can be classified into one of two categories: destructive edits and nondestructive edits. Nondestructive edits have clear advantages over destructive edits. This being the case, it is preferable to use nondestructive edits. Consequently, the purpose of this article is to look at nondestructive editing techniques and the improved image quality and flexibility that they provide.

Destructive vs. Nondestructive Edits

To better understand the difference between destructive and nondestructive editing, it is best to start off with the definitions of these two types of edits.

Destructive Edits: Destructive edits change the original image data.

Nondestructive Edits: Nondestructive edits do not change the original data.

Figure 1: Landscape Image

An example of each type of edit will help clarify these concepts. Figure 1 shows a landscape scene. It is obvious that the sky needs to be darkened a bit.

Figure 2: Tools Panel
One way to perform this edit would be to select the Burn tool from the Tools panel (see Figure 2) and apply the tool directly to the Background layer in the Layers panel (see Figure 3).
Figure 3: Layers Panel
This will produce the image seen in Figure 4.
Figure 4: Image with Darkened Sky -- Destructive Edit
As can be seen, the image in Figure 4, with the darkened sky, looks better than the original image. However, by editing in this manner, a problem has been created. The edit was performed on the Background layer. That is, the edit was performed on the original data. As a result, the original data has been altered. This is an example of a destructive edit.
Figure 5: Layers Panel with Burn Layer
Another way to darken the sky is to first duplicate the Background layer. For this image, the duplicated Background layer has been renamed as the Burn layer (see Figure 5). The edits are now performed on the Burn layer. Consequently, the edits are not performed on the original data. Thus, the original data remains unaltered. This is an example of a nondestructive edit. The image with the non destructive editing (see Figure 6) looks pretty much the same as the image that received the destructive editing, but it has the advantage of keeping the original data unaltered.
Figure 6: Image with Darkened Sky -- Nondestructive Edit

Advantages of Nondestructive Editing

Nondestructive editing has three advantages:

The first advantage of nondestructive editing is that the original data is preserved in an unaltered state. That way, the original data can always be accessed for future edits. On the other hand, if the original data is altered with a destructive edit, the original data is gone. Only the altered data exists. The only way to access the original data would be to undue every editing step or delete the image and start all over again with the original image (assuming that a copy of the original image was still available).

Another major advantage of nondestructive editing is flexibility. Nondestructive editing is performed using tools and techniques that usually allow for changes to the edits at any time. For instance, assume that the contrast in an image was edited early in the editing by adding a Curves layer (a nondestructive edit). Then, several other edits were performed. If it was later decided that the contrast was not quite right and needed to be changed, the Curves layer could be reedited to change the image contrast. Furthermore, the Curves layer could be reedited as many times as necessary until the contrast was correct, and there would not be any lose of image quality due to the reedits. Conversely, once a destructive edit is performed, it is burned into the image. The destructive edit can not be reedited at a late time. The only option that a photographer has with respect to altering destructive edits is to perform additional edits on top of the earlier edits.

The last advantage of nondestructive editing is image quality. To better understand how nondestructive edits produce higher image quality than destructive edits, imagine an image that undergoes the following edits:


The key point here is that almost all edits cause image degradation. This is true even for nondestructive edits. It is important to remember the definition of nondestructive edits: Nondestructive edits do not change the original data. The definition does not state that nondestructive edits do not degrade image detail. In fact, almost all of them do (Part III of this article series will deal with this in detail and will also cover the one editing process that does not cause any image degradation).

Now, in the case of destructive editing, each edit results in a separate instance of image degradation at the time the edit is made. For this image, there are six edits. So, if the image were edited with destructive editing, there would be six, separate image degradations. It is true that each image degradation would be fairly small. However, the image degradations would be cumulative.

The greater the number of destructive edits that are made to an image, the greater the total image degradation that will result. The problem here is that images that end up as fine art prints, or other high end uses, often have extensive editing. A single image can have many edits. If destructive editing is used in such cases, the total image degradation will likely be noticeable.

The situation is entirely different with nondestructive editing. While most nondestructive edits still create some image degradation, the image degradation does not occur at the time the edits are made. Instead, the degradation only occurs at the time the image is flattened or printed. Then, all of the edits are applied at the same time (at which point a single image degradation occurs). Therefore, even though the image mentioned above undergoes six edits with nondestructive editing, it is only degraded once when it is flattened or printed. This results in less image degradation that when destructive edits are used.

Nondestructive Editing Techniques

There are several methods of carrying out nondestructive editing. This article series will cover:

Nondestructive Editing -- Separate Image Layers

Figure 7: Create a New Layer Button

An image layer is any layer that contains image data. An image layer can be created in a number of ways (e.g., image data pasted from another layer or an image layer dragged over from another image). However, the most common way that an image layer is created is when a layer, such as the Background layer, is duplicated. This is done by dragging the layer to the Create a new layer button at the bottom of the Layers panel (see Figure 7).

Figure 8: Image Layer Added

After the layer has been duplicated (see Figure 8), the editing can be performed on the duplicated layer instead of the original layer. That way, the original data is not altered. Generally, a separate image layer is used for each edit. That way, the edits remain independent of each other. For example, the sharpening could be adjusted without affecting the color correction or contrast edits.

Figure 9: Mask Applied to Layer

The power and flexibility of image layers can be further increased through the use of masks. For example, at the beginning of this article, the sky of the landscape image was nondestructively darkened by burning on a duplicated copy of the Background layer (which had been renamed as the Burn layer). In Figure 9, a mask has been applied to the Burn layer to restrict the edits to the sky.

While separate image layers allow for nondestructive editing, they do have one disadvantage. Image layers significantly increase the size of a file.

Nondestructive Editing -- Neutral Layers

A neutral layer is a layer that is filled with neutral gray. A neutral layer, initially, has no image data and contains no tonal or color edits. However, a neutral layer provides a layer where further editing can be done.

Figure 10: New Layer Dialog Box

One of the easiest ways to create a neutral layer is to choose Layer/New/Layer. The New Layer Dialog Box appears (see Figure 10). In the dialog box, the Use Previous Layer to Create Clipping Mask option should be unchecked. The color should be set to None and the Opacity to 100%. When the dialog box first appears, the Mode will be set to Normal. With this setting, the Fill with Overlay-neutral color option will be grayed out and can not be selected. In order to create a neutral layer, one of the other Modes that will activate this option, such as Overlay, will need to be selected. Then, the Fill with Overlay-neutral color option is checked.

Figure 11: Neutral Layer Added
Clicking OK will create the new layer, which is now shown as a gray layer in the Layers panel (see Figure 11). However, the neutral layer currently has no effect on the image due to the Overlay Blend mode.
Figure 12: Burn Tool Used on Neutral Layer
The Burn or Dodge tools can now be used directly on the neutral layer. The neutral layer is simply selected and the Burn or Dodge tool applied to the area of the image where the editing is desired. Figure 12 shows the Layers panel after the Burn tool was use to darken the sky. Again, the original image data has been protected.

Nondestructive Editing -- Adjustment Layers

Figure 13: Adjustments Panel

One of the most common nondestructive editing techniques is the use of adjustment layers. Adjustment layers apply tonal and color edits to an image without altering the original image data. The adjustment tools are shown in the Adjustments panel (see Figure 13). The Adjustments panel provides access to the following adjustment layers: Brightness/Contrast, Levels, Curves, Exposure, Vibrance, Hue/Saturation, Color Balance, Black & White, Photo Filter, Channel Mixer, Invert, Posterize, Threshold, Gradient Map, and Selective Color.

Figure 14: Curves
Clicking on one of the buttons will add an adjustment layer to the Layers panel. For instance, clicking on the Curves button will launch Curves (see Figure 14 which has a curve applied). This adds a Curves layer to the Layers panel (see Figure 15). This Curves layer applies a nondestructive edit to the image.
Figure 15: Curves Layer Added

More Nondestructive Editing in Part II

In Part II of this article series, nondestructive editing with Smart Objects will be introduced.


Nondestructive -- Part II