Sixthcrusifix
28-03-2007, 23:37
Tutorial: Layer Masks and Channels in Photoshop.
Difficulty: Medium
Required knowledge: Basic Photoshop Proficiency and knowledge of Layers.
Category: Non-Destructive Editing.
One of the most common things you'll want to be doing in photoshop is isolating images from certain picture and compiling that image with other ones to form a new image. There are a host of ways to do this, including using some of the more dubious lasso and wand tools, which are 90% ineffective. I like to use a combination of selections through channels for accurate selections and masks for non-destructive layer hiding.
To do this I will first explain what a channel is.
First of all, you can find the Channels near the Layer palette. If you don't see it, Go to WINDOW>Channels.
The top channel is not really a channel, it's a representation of the three channels below it put together. It is followed by the Red, Green and Blue channels and then any extra Alpha Channels you may make.
Basically, the three primary colors of light are Red, Green and Blue. Each Pixel on your monitor is a little set of three light bulb like things, there's a red one a green one and a blue one. The color of the pixel is determined by how bright each light is. This is how the Hex code for colors in HTML works. Each color has a value of 0 (no color) to 255 (Full brightness). So if Red Green and Blue are all set to 0, it's black. If they're all set to 255, it's white. And there are 16 million colors in between. I could go on and on about these types of things, but let's skip ahead to channels.
In photoshop, your image is stored by Channels of color. There's a Red channel, a Blue Channel and a Green Channel. These channels are grayscale images. Grayscale images have 256 shades in them from black to white, are you getting the connection? Each channel is a map that tells photoshop HOW much of that color is to be displayed. Black stands for 0, none of that color. White stands for 255, all of that color. So if your Red Channel is completely black, there is NO red in that image, and that image is probably only green and blue (And what's in between). You can edit these channels to edit the colors in your image.
Now, these are the MAIN channels. But you can also make your own channel called an Alpha Channel. An Alpha channel is just a special hidden layer that is a grayscale image. These are used for selecting things. Black means 100% selected, white means 0% selected, The grays in between represent partial selection. You may know partial selection as "Feathering", it's when the edges are fuzzy and fade out.
The main reason to use a channel to make a selection is because it could be a lot more smooth and accurate. Let's say you have a picture of a red apple against a blue wall. You can go to your blue channel and you'll see that the apple is very black and the wall is very white. You can copy this channel into a new alpha channel, play with the contrast and then CTRL+ CLICK on the channel's thumbnail and you'll have an accurate and smooth selection!
And those are the Bare Boned basics of Channels and Alpha Channel Selections.
__________________________________________________ __________________
Now onto Masks!
Have you ever deleted something from an image and then an hour later you look at it and say "OH CRAP, I NEEDED THAT". If you just deleted the pixels, you're either going to have to traverse through your history forever and lose your current edits, or try to play with the history brush (IF It's not too far back in the history). Obviously it would be a lot better if you could just delete whatever you wanted and have the ability to bring it back instantly if you needed to. Well you can, with Layer Masks.
You can make a layer mask by clicking on the black circle button in the layer pallet. (It says layer mask when you hover in windows). Basically the layer mask creates a spacial channel for that layer that determines how much of that layer is visible. White means visible, black means invisible and all the greys in between represent partial visibility (opacity).
In this way you can paint on that channel in greyscale and have complete control over the opacity of each pixel on that layer. You can delete something, and if you need it you just grab a white paintbrush and bring it back. This is where those channels come in!
Remember how we can use those channels to make selections? We can also use those channels' black and white images as masks in photoshop. Then we'll have a smooth and accurate selection that hides the parts we don't want to see.
To do this you simply have to load the selection of the Alpha Channel to the layer mask. This sounds harder than it is, and there are two ways to do it:
1. The first way to do this is to just copy the Alpha Channel and paste it into the mask (The mask appears as a layer next to and attached to the layer you make it for).
2. The better way is to use the selection; Just hold CTRL and click on the Alpha Channel's thumbnail. Then go back to your layer and make a new mask, the mask will automatically hide the right parts. If the mask hides the opposite parts you want, just click on the layer mask and press CTRL+I to invert it. :)
I hope this inspires and helps you. This Tutorial will be 100% easier to understand when I include the images, in fact I could probably lower the difficulty level. But I'm not at my computer with Photoshop at the moment.
Difficulty: Medium
Required knowledge: Basic Photoshop Proficiency and knowledge of Layers.
Category: Non-Destructive Editing.
One of the most common things you'll want to be doing in photoshop is isolating images from certain picture and compiling that image with other ones to form a new image. There are a host of ways to do this, including using some of the more dubious lasso and wand tools, which are 90% ineffective. I like to use a combination of selections through channels for accurate selections and masks for non-destructive layer hiding.
To do this I will first explain what a channel is.
First of all, you can find the Channels near the Layer palette. If you don't see it, Go to WINDOW>Channels.
The top channel is not really a channel, it's a representation of the three channels below it put together. It is followed by the Red, Green and Blue channels and then any extra Alpha Channels you may make.
Basically, the three primary colors of light are Red, Green and Blue. Each Pixel on your monitor is a little set of three light bulb like things, there's a red one a green one and a blue one. The color of the pixel is determined by how bright each light is. This is how the Hex code for colors in HTML works. Each color has a value of 0 (no color) to 255 (Full brightness). So if Red Green and Blue are all set to 0, it's black. If they're all set to 255, it's white. And there are 16 million colors in between. I could go on and on about these types of things, but let's skip ahead to channels.
In photoshop, your image is stored by Channels of color. There's a Red channel, a Blue Channel and a Green Channel. These channels are grayscale images. Grayscale images have 256 shades in them from black to white, are you getting the connection? Each channel is a map that tells photoshop HOW much of that color is to be displayed. Black stands for 0, none of that color. White stands for 255, all of that color. So if your Red Channel is completely black, there is NO red in that image, and that image is probably only green and blue (And what's in between). You can edit these channels to edit the colors in your image.
Now, these are the MAIN channels. But you can also make your own channel called an Alpha Channel. An Alpha channel is just a special hidden layer that is a grayscale image. These are used for selecting things. Black means 100% selected, white means 0% selected, The grays in between represent partial selection. You may know partial selection as "Feathering", it's when the edges are fuzzy and fade out.
The main reason to use a channel to make a selection is because it could be a lot more smooth and accurate. Let's say you have a picture of a red apple against a blue wall. You can go to your blue channel and you'll see that the apple is very black and the wall is very white. You can copy this channel into a new alpha channel, play with the contrast and then CTRL+ CLICK on the channel's thumbnail and you'll have an accurate and smooth selection!
And those are the Bare Boned basics of Channels and Alpha Channel Selections.
__________________________________________________ __________________
Now onto Masks!
Have you ever deleted something from an image and then an hour later you look at it and say "OH CRAP, I NEEDED THAT". If you just deleted the pixels, you're either going to have to traverse through your history forever and lose your current edits, or try to play with the history brush (IF It's not too far back in the history). Obviously it would be a lot better if you could just delete whatever you wanted and have the ability to bring it back instantly if you needed to. Well you can, with Layer Masks.
You can make a layer mask by clicking on the black circle button in the layer pallet. (It says layer mask when you hover in windows). Basically the layer mask creates a spacial channel for that layer that determines how much of that layer is visible. White means visible, black means invisible and all the greys in between represent partial visibility (opacity).
In this way you can paint on that channel in greyscale and have complete control over the opacity of each pixel on that layer. You can delete something, and if you need it you just grab a white paintbrush and bring it back. This is where those channels come in!
Remember how we can use those channels to make selections? We can also use those channels' black and white images as masks in photoshop. Then we'll have a smooth and accurate selection that hides the parts we don't want to see.
To do this you simply have to load the selection of the Alpha Channel to the layer mask. This sounds harder than it is, and there are two ways to do it:
1. The first way to do this is to just copy the Alpha Channel and paste it into the mask (The mask appears as a layer next to and attached to the layer you make it for).
2. The better way is to use the selection; Just hold CTRL and click on the Alpha Channel's thumbnail. Then go back to your layer and make a new mask, the mask will automatically hide the right parts. If the mask hides the opposite parts you want, just click on the layer mask and press CTRL+I to invert it. :)
I hope this inspires and helps you. This Tutorial will be 100% easier to understand when I include the images, in fact I could probably lower the difficulty level. But I'm not at my computer with Photoshop at the moment.