Of the three basic Blur effects, Box Blur, Fast Blur, and Gaussian Blur, Box Blur is the most complex. It is similar to bot the Fast and Gaussian Blur, but it has the added advantage of an Iterations property, which allows you to control the quality of the blur.
To apply a Box Blur, go to Effect, Blur & Sharpen, Box Blur. As with other Blur effects, Blur Radius controls the amount of blur. Blur Dimensions determines whether to blur horizontally, vertically, or in both axes. Repeat Edge Pixels will preserve the edges of our footage when blur is applied. The Iterations property is what sets the Box Blur apart from the Fast and Gaussian Blurs.
You can see that as I increase the Blur Radius, our footage begins to get a rather boxy looking blur (set to 25). With a name like Box Blur, that is to be expected. This can create some pretty cool looks, if that’s what you’re going for. But the Box Blur is also capable of creating some very smooth blurs.
Increasing the Iterations of the blur will provide a more smooth result. So we currently have our Blur Radius set to 25. Turning the Iterations up to 2 means we will blur the image again by that same value. A higher number will create softer transitions between colors, but at the cost of increased render times. The maximum value of Iterations is 50.
According to Adobe, 3 iterations will give you a similar result as a Fast Blur. So let’s a take a look at our footage with a Fast Blur applied with a Blurriness of 25. Here is the same image with a Box Blur set at 25 and 3 iterations. This image is much blurrier, because we are basically blurring it by 25 three times. If we lower the Blur Radius to 9, the Box Blur becomes nearly indistinguishable with the Fast Blur.
Between the Box, Fast, and Gaussian Blurs, you really can’t go wrong with Box. Fast Blur has its merits, but the Box Blur can replicate the Fast Blur and more.