Learning from channels in Photoshop
Video: Learning from channels in PhotoshopBefore we actually go to the steps of creating an opacity mask inside of Illustrator, I thought it would be helpful to first get a better understanding of how channels work inside of Photoshop, and also how layer masks work inside of Photoshop. Now if don't have Photoshop open right now, that's quite all right. I'm just going to give you a basic overview of some of these settings. In reality, if you want to learn everything there is to know about channels inside of Photoshop, definitely check out Channels and Masks by Deke McClelland. But for now I just want to cover some basic concepts.
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In this installment of Illustrator Insider Training, Mordy Golding shows experienced Illustrator users how to create transparency effects and ensure reliable printing results. This course reviews the history of vector transparency and covers features such as knockout groups, opacity masks, and transparency flattening. Mordy also shows how to establish a safe workflow when placing Illustrator graphics containing transparency in PostScript, PDF, and InDesign files. A free worksheet is included with the course.
- Understanding how transparency works across the Adobe applications
- Deconstructing the Transparency panel
- Adding transparency to gradients
- Understanding how overprints and knockouts work
- Using a gradient or complex appearance as an opacity mask
- The rules of transparency flattening
- Working with complex regions
- Understanding the relationship between flattening and stacking order
- Creating and sharing flattener presets
- Saving PDF files and using the PDF/X standards
Learning from channels in Photoshop
Before we actually go to the steps of creating an opacity mask inside of Illustrator, I thought it would be helpful to first get a better understanding of how channels work inside of Photoshop, and also how layer masks work inside of Photoshop. Now if don't have Photoshop open right now, that's quite all right. I'm just going to give you a basic overview of some of these settings. In reality, if you want to learn everything there is to know about channels inside of Photoshop, definitely check out Channels and Masks by Deke McClelland. But for now I just want to cover some basic concepts.
Really, if you want to think about it, it's just about making selections inside of Photoshop. Let me explain to you what I mean and this is all going to make a lot of sense when we apply this knowledge to working with opacity masks back inside o Illustrator. Right now I have this file opened up. it's called glories.psd, and it's a regular plain file with no opacity in it whatsoever. In fact, I see over here I have a single Background layer with a lock icon on it. That means I can't really work with any transparency on this layer. So the first thing I'm going to do is I'm going to set this to a regular layer inside of Photoshop. I'm going to double click, not on the name itself because that will allow me to rename the layer. I'm just going to double-click on this blank area right here.
That's going to bring up the New Layer dialog box and I'm just going to click OK. And notice now that it changes it to Layer 0 and the lock is gone. Another way, by the way, to do that. I'll just press Undo, a little shortcut here. I'm going to hold down the Option key on my keyboard. I'm on a Mac, so if you're on Windows that would be the Alt key and then simply double-click on a blank area and that automatically sets that now to a regular layer that can support transparency inside of Photoshop. Now if I look at my Channels panel right over here, I see that a regular image inside of Photoshop here, this is an RGB image, is made up of three channels: a red channel, a green channel, and a blue channel.
Photoshop also presents us with an RGB channel or what we call a composite channel, so I can see all these combined together for the final image here. Now the reason why I'm showing these to you is because one of the most powerful things to do inside of Photoshop is to make selections. So for example, if I go back let's say to this tool right here, the Rectangular Marquee tool, and I go ahead now and I click and drag to draw with let's say a selection around this area, if I go to the Select menu here and I choose to save that selection, and I call this one rectangle and I click OK, you can see that now that I've done that, a new channel has been created inside of my file.
Now let's click on the channel to see exactly what that is. I'm going to hit Command+D or Ctrl +D to hide my selection here and basically what Photoshop did, it doesn't save any paths. You know, these are just pixels here. Photoshop took that marquee area that I drew before and turned that now into a channel. That channel is made up of white pixels and black pixels. So now if I ever want to load that selection again, Photoshop would just say hey, whatever pixels are white become selected. Whatever pixels are black don't become selected.
But as you can see here it's kind of added here as a channel inside of this document. Now I can use a channel for a variety of different things. One thing that I can use it for is actually to make a mask. So let me show exactly what I mean by that. I'm going to hold down my Command key. I'm on a Mac computer here. So again, if you're on Windows, that would be the Ctrl key. I'm going to move my cursor over this thumbnail right here. See that little kind of like a hand with a little marquee area it shows up? If I go ahead now and I Command+Click or you can Ctrl+Click on that area, then Photoshop loads that selection now.
So notice you can see the marching ants in my screen. I'm going to go back to my Layers panel. And with Layer 0 right now selected right here. You can see that I have it now currently selected. I'll come down over here to the bottom of my Layers panel and click on this button over here, which allows me to turn that selection now into a layer mask. Notice what happens over here, I have a new icon here. The icon basically now shows what my channel was-- remember, or my selection-- and basically whatever pixels were white, allows me to see my artwork through those areas. But whichever part or whatever pixels were black, then that part of the image is no longer visible.
Those now are hidden by the mask. Now if we think for a moment here about clipping masks that we make inside of Illustrator, I can take a rectangle, I can put that rectangle on top of an image, and I can tell Illustrator to make a clipping mask of that rectangle. That means that anything inside of that rectangle is visible. Anything outside of that rectangle is not visible, which is also the same thing that we see here. So if we just imagine for a moment that my channel that I had here inside of Photoshop was really a vector object, anything inside the bounds of that white rectangle is visible.
Anything outside the bounds, which is now colored black, becomes invisible, so I can't really see the image that's there. Of course, working inside of Photoshop, however, the whole image is there. I haven't damaged any pixels. That's the beauty of working with these layer masks here inside of Photoshop. Now I'm going to actually press Command+ Z or Ctrl+Z to undo that for a moment, because I want to go back to the channels here for a second. And I'm going to click on this rectangle here. I'm going to press Command+D or Ctrl+D to go ahead now and get rid of my selections. So now I'm just looking at this rectangle channel.
Right now I have either white pixels or I have black pixels. The real power of Photoshop is that this channel, which is really if you think about is just the selection, has the ability to have multiple levels of gray. In fact, this channel because it's 8-bit can have 256 levels of gray. So I don't have a choice of only things that are completely visible or completely invisible, but areas that are colored gray become partially visible. So let me show you exactly what I mean by that. If I go now to the Filter menu here and I choose Blur and I choose Gaussian Blur and let's say I choose a Radius of around 30 pixels, so notice over here now I don't really have just completely black and white pixels. I also have different levels of gray inside of this channel.
Now let's perform the same steps. I'm going to hold down the Command key. Again, Ctrl on Windows. I'm going to click on this thumbnail here to load that selection. Now let's go ahead and click on RGB here. I'll go to Layers. Make sure that I'm clicking on Layer 0 and now I'm going to activate a mask. But notice now that I don't have those hard edges. Now my image kind of has a vignette. It kind of feathers out as I see that image there. So the mask doesn't just have a hard edge; the mask now has a soft edge. But again, what makes that work is that the mask is simply made up of various levels of gray.
Anything that's completely black I can't see through, anything that's white I can see through, and anything that's gray I can kind of see through. Now if you think about the clipping mask that we make inside of Illustrator, there's really no way to do that. I mean you have a vector path. Anything that's in the path is visible. Anything outside the path is not visible, so you can never get a soft edge. That hard sharp vector line defines what is and what is not visible. But in the world of opacity masks, however, we can create this exact effect and we can do it inside of Illustrator.
That's because an opacity mask is exactly like a layer mask, like we've seen right here inside of Photoshop. An opacity mask is not a vector path. An opacity mask is some type of image or a piece of artwork and the grayscale values of that artwork or of that image become the mask. They define what is and what is not visible. So now that we have this understanding about how these layer masks work inside of Photoshop, in the next movie we'll go back to Illustrator and we'll see how to create this type of effect using the opacity mask.
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