Join Deke McClelland for an in-depth discussion in this video Understanding selections and layers, part of Learning Photoshop for Design (2011).
In this exercise I am going to introduce you to two concepts that go to the heart of using Photoshop and those are selections and layers. We are going to start things off in this file called Faces flat.jpg, found inside the Exercise Files folder. Anytime you open a JPEG image you are opening a flat file, that is to say it contains no layers whatsoever, and to confirm that go over here to Layers panel, which by default exists in the lower-right corner of the screen. If you don't see it you can go up to the Window menu and choose the Layers command or you can press the F7 key.
That shortcut, F7, carries across many of the Adobe Creative Suite applications. Assuming that you have the Layers panel on screen, notice there's just one item at work inside this image and it's called Background. The background by definition is not actually a layer. It's a rectangle that measures so many pixels wide by so many pixels tall. But that's all it contains pixels and only pixels, which makes it a little bit tricky to work inside of your image. For example, we are looking at an image that contains five differently colored spheres. If this were some sort of strange real-world scene and I were to ask you to select the blue sphere, then you would reach out and touch this sphere right here. In fact any child or infant could distinguish the blue sphere from the ones around it.
However, Photoshop is not so capable as a child or infant and it doesn't see that definition nearly as well, and here is why. Let's say I decide to go ahead and zoom in on this transition between the blue sphere and the green sphere and I'll do so by pressing Ctrl+Spacebar or Command+Spacebar on the Mac and then dragging to the right. Once I've zoomed in sufficiently far, and I happened to have zoomed into 2600%, I will see the pixel grid on screen, which are these white lines that distinguish one square colored pixel from its neighbor, but even at this area of rapid contrast which is known as an edge inside of Photoshop, you can see that 1 pixel is remarkably like its neighbor. So we have a light blue pixel right there, next or we have a kind of medium blue pixel, then above it is a darker blue, but we're still looking at blue ultimately and it takes a couple of more pixels to start transitioning over to green.
This is what's known as a continuous tone image inside of Photoshop. In other words, we're not seeing objects the way we would in Illustrator or InDesign. We are seeing gradually transitioning pixels. I will go ahead and press Ctrl+0 or Command+0 on the Mac to zoom out. Let's say that I want somehow to select his blue sphere and remove it from its background. Well I might have a fair amount of luck using this Elliptical Marquee tool and you can get to this tool by clicking and holding on the Rectangular Marquee tool second down in the toolbox and then choosing the Elliptical Marquee tool from the fly-out menu.
Then I might drag around that sphere like so. I am not going to nail the sphere just by dragging with this tool; fortunately you can register your selection outline on the fly as you drag it by pressing and holding the Spacebar. That allows you to move the selection outline independently of the image as you're making it. With the Spacebar down I will go ahead and register the top and left edges of that selection outline like so, then I will release the Spacebar and continue dragging until I've surrounded that blue sphere.
Now at this point I have selected the image. If I were to set in dragging this selection to a different location I'd move the selection outline not the selected pixels. If I want to move the selected pixels instead, I will press Ctrl+Z, Command+Z on the Mac to undo that modification and then I will switch to this very first tool in the toolbox, the Move tool. Then I'd go ahead and drag inside the selection outline to move it and you can see the problem. Even though I've done a pretty darn good job of moving that selected sphere to a new location, I have left a hole in the background and there's no context for that hole.
Photoshop goes ahead and automatically fills it with the background color, which is this bottom color in the toolbox, which by default is white, because it has no way of knowing what should be behind that sphere. For example it doesn't know what the right edge of the screen sphere should look like or the left edge of the red sphere or what have you. Let's go ahead and compare that to layers. I am going to switch over to this image right here. It's called Face layers.psd. It's the exact same image. It looks just the same as the other one on screen. However, it's put together very different.
This is a native Photoshop or PSD document and PSD files can contain layers and you can see what those layers look like by going over to Layers panel once again. We've got a background item, which is the big flat rectangle that measures so many pixels wide by so many pixels tall, and then we have a series of floating layers sitting on top, beginning with violet at the back and going all the way up to blue toward the front. Now when I'm working with a layer, I don't necessarily need to create a selection outline in advance. Using my Move tool, which is still selected at the top of the toolbox, I could just go ahead and grab the active layer.
So first thing I need to do is click on the layer here inside the Layers panel that I want to modify, I'll go ahead and click on blue, and then I would drag it to a different location like so, and notice now that I'm not leaving a background colored hole in my wake; instead I'm revealing in this case the right edge of the green sphere, the left edge of the red sphere, and so forth. I can even move layers up and down the stack. So if I go ahead and put the blue sphere right there let's say, now I want it to appear behind the red sphere, and I could just go ahead and grab the blue sphere and move it behind the red sphere here inside the Layers panel.
Now I don't mean for a second to imply that somehow selections are inferior to layers; in fact you oftentimes need selection outlines to create layers in the first place. But now that you have a sense for how selections and layers work inside Photoshop, you're ready to begin using the program in earnest.
- Getting around an image
- Creating accurate selections
- Creating a layered composition
- Scaling and rotating layers
- Creating realistic layer effects
- Painting with the brush tool
- Tracing outlines with the pen tool
- Creating editable effects with smart filters
- Saving an image and preparing it for print