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.
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.
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.
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:
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.
There are several methods of carrying out nondestructive editing. This article series will cover:
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).
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.
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.
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.
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.
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.
In Part II of this article series, nondestructive editing with Smart Objects will be introduced.