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- 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
Skill Level Intermediate
Okay, so now we understand exactly what a knockout is inside of Illustrator. Again, it's a default behavior whenever you're dealing with overlapping objects with different colors, where the top object knocks out or removes the actual part of the object that exists directly beneath it. That prevents colors from mixing on press, giving us unwanted color changes. However, in the world of transparency, the whole concept of knockout is completely different. Because if you think about it, if I take let's say just this shape right here and I'm working on this file here called flower2.ai, and I select this element right here and I choose to actually make it transparent by maybe applying an Opacity of 50%, so now I'm telling that object to only be 50% in opacity.
What does that mean? That means I won't be able to see through that object and obviously I want to see through it to see what appears beneath it. I mean that's the whole point of transparency-- the ability to actually see through an object and to see what's behind it. Now if the default behavior of Illustrator is to actually knockout the actual blue behind it, I wouldn't see a green color here because the blue part would be gone. So when I'm using transparent effects inside of Illustrator, there actually is no knockout going on at all. The object that appears beneath it is there and I can see through the front object to the objects that appear beneath it.
So if you want to think about it again from the terminology that we spoke about in the previous movie, whenever you're using transparency, by default that object is always going to really overprint the object so that you can see through it and see what's beneath it. But there may be times when you don't want that behavior. So let's, for example, see what happens here. I'm actually going to take these two elements right now. Remember this object right now has 50% opacity applied to it. So now it looks like it's kind of like there's a green color over here, because I'm seeing the yellow and the blue mixing, which gives me this particular appearance.
I'm going to select both elements right now and I'm going to group them together. Command+G on the Mac or Ctrl+G on Windows. It's important to realize that the Knockout Group setting which we're going to apply here obviously only works on groups. That's why it's called Knockout Group. So the two settings that we've seen over here, Isolate Blending and Knockout Group so far, only apply when I'm using these settings on a group. Now you can see over here that by grouping these together, the Knockout Group setting now has a line through it here. This is actually an important thing to note about working with Illustrator.
There are actually three states over here of this particular checkbox. I can either have it unchecked or completely disabled. I can have it checked, meaning that it's now enabled, or I can have it now kind of like semi-checked. In other words, it's highlighted, there's a line through it, but it's not completely checked. The engineers at Adobe call this a neutral setting and in a minute we'll understand exactly why that setting exists. But for now, if I want to turn on the Knockout Group setting, what I'll do is I'll actually click on this right now and now there's a checkbox here, and take a look at my result.
What I'm basically seeing right here is that the yellow object actually now knocked out the blue that appears beneath it. Now we can actually get a better idea about what these results actually did here by turning on the Transparency Grid. So I'm going to go to the View menu here, I'm going to choose Show Transparency Grid, and you can see now that this circle right here, which I've applied 50% Opacity to-- Again, if I use in my Direct Selection tool, let's deselect it and just select only select the yellow circle right here. This circle has an opacity of 50%.
And I have the blue shape that appears beneath it. You would normally think that I'd be able to see through the yellow shape and see the blue beneath it, which would make my object turn green. But because now I've turned on the Knockout Group setting for this group, I've instructed Illustrator to take the objects with transparency right now and actually use those objects to knockout the objects beneath them, meaning I don't want to see through the object to what appears beneath it. I want to see through the object all the way through to the bottom of the stack, which in this case is my transparent background.
Now I'll switch back to my Regular Selection tool here and just actually select the entire object so we can see the Knockout Group setting is on. If I click on the checkbox to turn it off, now I see what this artwork looks like. The blue is actually there and I can see through the yellow to the blue when I get a mixture of those two colors. But by turning on the Knockout Group, again I have to click twice now, because the first time gives me the Neutral setting and the second time gives me the Knockout Group setting. Now I'm actually punching out or knocking out the artwork that appears at the bottom of this group, so that the objects on top that have opacity are actually able to be seen straight through and through.
Now let's for a moment here talk about this neutral setting. I'm going to click twice over here, so now my checkbox is set in this neutral setting. This is Illustrator's default. Because if you think about it, the way that I structure my groups inside of Illustrator, I may have many many different overlapping groups and I can have nested groups, meaning I have groups within other groups and within other groups. Adobe doesn't ever want there to be a situation where I just simply group something together and then there's a change in my appearance, because the Knockout Group setting can actually occur on many different levels.
For example, let's say I have three groups and those three groups are found inside of another group. I can have the Knockout Group setting on the parent group and those obviously effect the groups inside of them. So I don't really ever want to be in a situation where just by grouping something, I actually go ahead now and change its appearance. If you've seen Illustrator Insider Training: Rethinking the Essentials, you already know how important groups are and structures are inside of Illustrator. So Adobe doesn't want to get into a situation where I create a group and make a change in the appearance of the art. So that's why. Because Illustrator doesn't know if I want that artwork to knockout or not, It turns that group into a neutral setting.
And if you think about it, what neutral really means is that Illustrator ignores the fact that these two objects are actually in a group. From a transparency perspective, Illustrator makes believe that these two objects exist on their own. So they obviously don't knock each other out from a group perspective, because from Illustrator's thinking, these two elements are not grouped together. But if I know that I wanted these objects to actually knockout, I would turn on the Knockout Group setting and get this result. So it's kind of interesting if you think about it. If you remember that we spoke about knockouts and overprints for regular artwork, this is actually the complete reverse when we talk about transparency.
Illustrator's default behavior is always knocking out other artwork. If I want artwork to actually overlap and see through it, I would set it to Overprint. Well, when I'm dealing with transparency, elements normally overprint. But if I want to be able to knockout the objects beneath it, I turn on the Knockout Group setting. Now I know all of this may sound somewhat technical, but it would also be helpful to know how might you actually apply this kind of setting to artwork that maybe you create on a day-to-day basis. Well, we'll see a great example of that in the next movie.