What is a layer?
Layers are ways you can stack several images together or you can use them to apply changes to an image. Layers can be added, removed, duplicated, drawn on, moved around and edited independently of each other. It also means that we can work in a none-destructive way for example, if you painted over an image but decided you didn't like it, if you did it on a layer you could simply remove the layer and start again. It means you're always left with the image you started with no matter how many changes you make to it IF you use layers.
One of the easiest ways to understand them is to visualise them as glass windows with different things written on them.
Take a look at this example:
The white slide is the background then we add a layer and colour it black which you can see is the second slide and finally we add a second layer and draw a number two on it which makes up the final slide in our sequence.
How do you create a layer/control them?
The Layers Palette is where you can view all the layers you've created, create a new layer, duplicate a layer, delete a layer and make changes to the blend mode and opacity – something we'll discuss shortly.
Make a new layer
Once you have an image open in Photoshop click on the new icon (number 1) and a new layer will be added into the layers palette. You can now add things to this layer, draw on it etc. and it will not change the layer (your image) bellow it even though you can still see it, just as if you were drawing on a piece of glass. Do note that to work on a layer it needs to be 'active' which you do by clicking on it. When you do it will turn blue to let you know this is the layer you've selected to work on.
Name your layers
When you begin to add more and more layers to the palette having them named 1, 2, 3 will get confusing so it's best to rename them as you create them. To do this simply double-click on the name of the layer you want to rename in the layers palette and, as in the example, the layer name will now be highlighted in blue and will be sat in a text box so you can edit it. Pick a name that will remind you what the layer's for then click out of it for the name change to be complete.
Most of the time you'll want to copy a layer (usually your original image) so if you make changes you don't like, you always have the original image to go back to. To do this, drag your layer over the new layer icon (number 1 on the top image), or go to Layer>Duplicate Layer.
If you need to delete one of your layers, make sure it's selected then you can drag it down to the rubbish bin icon (number 2 on the top image), or go to Layer>Delete>Layer.
Show/Hide a layer
If you want to work on a layer but another one is blocking your view so you can't see what changes you're making simply click the eye icon to the left of the layer and it will be hidden from view. To bring it back all you have to do is click the eye icon again. It's a useful way to remove a layer you're not sure about without actually deleting it completely.
Move the layer order
Working on separate layers gives you the option to move them around. To do this, make sure you have the layer you want to move selected (so it's blue), select the Move tool then click and hold your left mouse button over part of the image and drag the layer. In our example we've moved the text from the bottom of the shot to the top. As a side note, if you have another tool selected you can hold down the Cntrl key on your keyboard to move a layer around.
To change the layer order in the palette, click on the layer you want to move and simply drag it up or down the layers palette.
Part two of this tutorial covers layer styles, blending modes, layer masks, groups and adjustments. Click on the link to view it: Photoshop Layers Tutorial Part Two.
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