Join Tim Grey for an in-depth discussion in this video Anti-aliasing, part of Photoshop: Selections (2011).
Anti-aliasing is a concept that applies at the pixel level, which might lead you to believe that it's too small an issue to be important. And yet it really can make a big difference in the overall quality of your selections. In this lesson we'll explore the concepts of anti-aliasing, so you'll have a better understanding of why you'll likely want to put this feature to use whenever possible with your selections. Selections are a way of defining which pixels should be affected and which should not be affected by a particular adjustment in Photoshop. Because pixels, at least generally speaking are square, a selection that goes along a diagonal, must of necessity take a zig zag path as it follows the edge of the pixels along that boundary.
Anti-aliasing helps smooth out that zigzag. Let's take a look with this blank canvas. I'll go ahead and choose the Polygonal Lasso tool and make sure that my Anti-alias option is turned off. I'll then draw a triangular selection which includes a horizontal line, a vertical line, and then a diagonal. After closing that Selection, again Anti-alias option turned off, I'll go ahead and fill that triangle Selection, with black, my foreground color. Now I'm going to create a new Selection, so I'll deselect my existing selection, and turn on the Anti-alias option.
I'll go ahead and Click, and Click to draw a vertical line and then click again to draw my horizontal and I'll go back to my original starting point to close out that selection. Again in this case with Anti-alias turned on. I'll go ahead and fill that triangle with the same black and we'll zoom in to get a closer look at the result. As you can see the diagonal for the triangle that did not have the Anti-alias option, looks rather jagged. That's because all pixels were either selected or deselected.
With the other triangle, using the anti-alias option turned on, you can see that the edge as being smooth. Instead of just black or white pixels, we have some shades of gray in between. And that's because, instead of simply choosing pixels to be selected or deselected, there are partially selected pixels along the way. And that helps to smooth out the overall transition along the edge of selections. Ani-aliasing only relates to selections that follow a path that is other than horizontal or vertical.
While that may mean anti-aliasing isn't applicable to all selections as far as I'm concerned whenever anti-aliasing is an option for a selection it should be put to use.
- Adding, subtracting, and intersecting
- Saving and loading selections
- Using Deselect, Reselect, and Hide
- Selection tools
- Advanced selection techniques
- Refining selections
- Selection projects