Gaussian Blur is dead long live Lens Blur! We're going to show you how to use the rather forgotten and neglected 'Lens Blur' tool in Photoshop combined with a layer mask to create a really effective peel-away shadow effect to give a bit of added depth and dimension to your designs.
The great thing about the Lens Blur tool is that you can simulate variable blur depth simply by using a layer mask to define the areas of your layer to blur and the 255 colour stops between white and black define the amount of blur. This has some really great uses, not least the ability to simulate the photographic Tilt Shift effect to give photos a really nice miniature effect.
So let's start...
First off you'll need to produce a layer/object in Photoshop that you can apply the peel shadow to, here we've created a simple ribbon using Photoshop's vector drawing tools to create a Shape Layer, and shifted the left side up with a bit of curvature for our peel away section.
Fill your Shape Layer ...
... and add a linear gradient layer style to add some depth for the curved part of the layer
Now we are going create the base shape for our shadow, you use either the vector tools to draw a shape layer or use the marquee tool. Draw a shape to the base of your ribbon layer that curves down to the bottom slightly and tapers in slightly underneath the ribbon shape like below:
Fill the layer and if you're using a vector shape layer, once you are happy with the shape rasterize it.
Next, apply a linear gradient mask to the layer that will be used as the basis for our lens blur effect, this part can be tricky to get right and will ultimately affect your final rendered shadow, so you might find yourself coming back to this point and adjusting to find the angle for the gradient.
Now we're ready to go into the lens blur, first though, make sure you select the 'layer thumbnail' part of the layer and not the mask. Then goto menu option Filter » Blur » Lens Blur, if you are using a shape layer it will ask you to rasterize the layer before proceeding.
You should see the Lens Blur filter window appear like below.
The actual settings here will vary depending upon your document dimensions. As a guide from the example here, our document dimensions are 548x250.
Set the mode to "More Accurate" for better rendering quality, and make sure you have "Layer Mask" selected in the "Source" dropdown.
The Blur Focal Distance is set at 255 (to cover the full black to white 8bit colour range).
The "Invert" checkbox is important, depending upon how you applied your linear gradient mask you may need to invert to get the blur at the desired end of the gradient range.
The "Radius" controls the amount of blur, set here to 24. All other options have been left at default.
Once you are happy with the preview select "OK" and you should get a nicely rendered blur shadow for your peel away.
And there you are. Embellish your ribbon, add to your design, job done.