What is an opacity mask?
Video: What is an opacity mask?In Illustrator you may already be familiar with something called a mask and you're probably familiar with something called a clipping mask. That's where you can take some artwork and place it within the bounds so that it's only visible inside of that shape. However, Illustrator also possesses a far more powerful mask, something called an opacity mask. Now before we actually learn how to create these opacity masks, I wanted to take a moment to first explain what exactly an opacity mask is, what makes it different than a clipping mask.
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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
What is an opacity mask?
In Illustrator you may already be familiar with something called a mask and you're probably familiar with something called a clipping mask. That's where you can take some artwork and place it within the bounds so that it's only visible inside of that shape. However, Illustrator also possesses a far more powerful mask, something called an opacity mask. Now before we actually learn how to create these opacity masks, I wanted to take a moment to first explain what exactly an opacity mask is, what makes it different than a clipping mask.
So let's take a look at this example right here with a document that I have open. It is called opacity_masks.ai. And on the bottom of my page over here I have these two circles here. This circle and this circle, which are both masks, and inside of that mask I have an image. It's the same image of these beautiful morning glories. Now this shape that's actually being used to create the masks in both of these examples is this shape over here on top. If I click on it, it's a regular plain vector object, but it has a Gaussian Blur applied to it that gives it that blurry appearance.
I can actually click on the Gaussian Blur effect here in the Appearance panel and see that it currently has a Blur set of 30 pixels. Now the important thing to realize here is that at the bottom of my page, I've used that circle to create these two masks, but you can see that I get two very different appearances as a result of those masks. That's because the circle here on the left is created used a regular plain clipping mask. What a clipping mask does is it takes the actual vector path itself and it uses that vector path to determine which parts of my image are visible and which parts of my image are not visible.
So anything inside of the path is visible. Anything outside of the path is not visible. Now if we take a look over here at the mask on the right, this was created using an opacity mask. An opacity mask uses the same shape but it doesn't really care at all about the vector path itself. What it cares about is the actual appearance of that path. More specifically, it takes the luminosity values of that object and uses that as the mask. Now, don't worry if all this sounds very technical, because throughout this entire chapter we're going to go step-by-step and we're going to understand exactly how opacity masks work and how we can use them to perform a variety of different tasks.
For example, I'm going to open up my Artboards panel here inside of this document. Right now I have an artboard called opacity_ mask, which is what I'm looking at right now. But I'm going to double-click on Mask Examples. This is going to take me to a different artboard in this file. Just want to show you here these are two possible examples of how you might think about using opacity masks. Over here on the left I have an image. In the middle area over here I have this regular plain gradient and then on the far right I have what happens when I use this gradient as an opacity mask for this image.
Notice over here that the image completely fades out to transparent. Let's take a look at this example here at the bottom. I have some regular vector artwork. I have an image that I've brought now into Illustrator. It's an embedded image that I brought in from Photoshop and I used that image as an opacity mask to make it look as if that image has kind of parts of it eaten away, almost like a distressed pattern. I'm going to zoom in over here so you can take a better look at that artwork. You can see how parts of the artwork are simply not there. You can see background right through it. So as you can see there are many different ways that I can actually use opacity masks inside of Illustrator.
They are incredibly powerful and once we learn a few simple concepts, we'll be able to use these opacity masks to solve everyday design problems inside of Illustrator.
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