A Word of Warning

As a print designer, the biggest challenge when working with filters is maintaining the willpower not to overdo it. Alot of the filter effects can completely change the overall appearance of your image—so use them with caution. It’s always best to use creative restraint and apply them tastefully. Another caution is that filter effects, unlike the layer styles discussed earlier, are by default, not “live” or nondestructive unless applied to a smart object. This means that if you forget to convert the image into a smart object  before applying filters, they will permanently alter pixel information. If not applied to smart objects, the only way to reverse a filter effect is to apply the Edit --> Undo command before you close the file.

To apply a filter to all the image information in a multilayered composition, the image must also be flattened or all the layers must be converted into a smart object. Therefore, to protect and preserve your pixels and layers, it’s always a good idea to experiment  with filters on a merged layer or on a duplicate, flattened version of your composition before saving your changes.

Creating a Merged Layer
To create a merged layer, select the layers in the Layers palette, and then while holding down Option/Alt, choose Merge Layers from the Layers palette flyout menu. Doing so creates a merged layer and leaves the selected layers intact. The merged layer appears above the topmost selected layer in the palette.