Next on our list of features we might want from Photoshop is adjustment layers. This gives Photoshop the ability to do non-destructive edits, an important benefit.
As mentioned previously, when you make an edit, that is numerical calculations done with the data stored in computer memory. Suppose you don’t like an edit you have made. You can dial it back or hit “Undo”. Now the computer has made 2 calculations: one to make the edit, and one to return to where you started. Will the data in memory be exactly the same as when you started? No – remember the problem with round off errors. So data is said to be “destroyed” because you don’t have your original back in exactly the same state. Do this enough times and you have a posterized or pixelated photo.
How Layers Solves the Problem
When using layers, this problem does not happen. Your original exists as the bottom layer and is untouched. You create a layer above this, and do your edits there. That layer is separate data in memory. All calculations are done on that data and not the original. You see the result of the edit, and you can twiddle back and forth to your heart’s content without affecting your original. Later, when you save, you can make a “flattened” copy that incorporates the effects of your edits into the final file.
Other Benefits of Layers
There are added benefits as well. If you save an “unflattened” copy first, with any layers you have made, you now have a record of what you did. You can also go and change any of the edits easily if you have changed your mind about something. Layers also allow you to composite one photo with another, perhaps to put the sky from one photo into another. Blending modes allow for creative choices when compositing.
Non-destructive Editing and Layers without Photoshop
I hope I have described non-destructive editing well enough that we don’t have to discuss whether you need it. You definitely need it. Can you get it without Photoshop? As you surely suspect, the answer is yes or I would have no reason to write this article. Photoshop Elements and GIMP both have layers. Photoline also appears to have layers, but I have not looked at the program yet.
Lightroom does not have layers, but implements non-destructive editing in a different way. The details of your edits are stored in a small file. Lightroom shows you what the results will look like, once you create an exported file. Your finished photo does not actually exist on the hard drive until you do the export. The develop module displays what you have done and can be changed easily. You cannot composite photos in Lightroom.
Picture Window Pro (PWP) also does not have layers, yet is non-destructive. In this case the program creates a new copy of the image in memory and works on that. If you like what you get you need to save the edited version if you want to keep it. As you work on an image you generate a new copies in their own windows, hence the name of the program. You can save a “workflow”, which will be a record of what you did and also can be changed later. PWP has operations which allow for compositing and stacking photos, and it has blending modes.
In Case You are not Convinced
I’m going to elaborate on this a bit more, because you may meet someone exposed to too much marketing who is certain that you need layers to have non-destructive editing. Their reasoning is something like this: “If I have layers, I have non-destructive editing. So if I don’t have layers, I don’t have non-destructive editing.” This seems compelling, but is a mistake in reasoning. I will give you the exact same reasoning but with an easily understood situation: “If I am in my kitchen, I am in my house. So if I am not in my kitchen, I am not in my house”. There are more ways to be in your house, and there are more ways to have non-destructive editing.
In the next installment we will look at color management.