Making Corrections with Daily Filters in Photoshop

Filters have a long and glorious history, ranging from performing essential tasks like removing abrasive particles from the oil in your car’s crankcase to even more important chores involving the pixels in your Photoshop images. In both cases, filters seize tiny, almost invisible, bits of stuff and rearrange them in useful ways. The results are something you’d never want to do without. Within Photoshop, filters (also called plug-ins because they can be installed or removed from Photoshop independently) can help you in many ways. They correct imperfect images, improve your best photos, or transform an object from one thing into another. Filters can mimic artistic painting styles, blur things that are too sharp, sharpen things that are too blurry, or create brand new objects (like clouds) that didn’t exist before. Just because all filters are plug-ins doesn’t mean that all plug-ins are filters. You’ll find plenty of plug-ins out there that have nothing to do with filters — or image editing, for that matter.

You Say You Want a Convolution?
All filters do one simple thing in a seemingly complicated way: They make Photoshop do your bidding. Deep within a filter’s innards is a set of instructions that tells Photoshop what to do with a particular pixel in an image or selection. Photoshop applies these instructions to each and every pixel in the relevant area by using a process the techies call convolution (creating a form or shape that’s folded or curved in tortuous windings), but which we normal folk simply refer to as applying a filter.

Corrective and destructive filters
Filters fall into two basic categories, corrective and destructive:
- Corrective filters fix problems in an image. They fine-tune color, add blur, improve sharpness, or remove nastiness like dust and scratches. Although corrective plug-ins can be fairly destructive to certain pixels, in general, they don’t change the basic look of an image. You might not even notice that a corrective filter has been applied unless you compare the new version of the image with the original.
- Destructive filters tend to obliterate at least some of an image’s original detail (some to a greater extent than others) as they add special effects. They may overlay an image with an interesting texture, move pixels around to create brush strokes, simulate light and shadow to create 3-D illusions, or distort an image with twists, waves, or zigzags. You’ll often be able to tell at a glance that a destructive filter has been applied to an image: The special effect often looks like nothing that exists in real life. An unaltered image can be improved by using a corrective filter such as Unsharp Mask (center) or changed dramatically with a destructive filter such as Find Edges (right).

Filter basics
Whether a filter is corrective or destructive, it is one of a couple of flavors — boring or super cool. (I made these names up myself. Can you tell?) Seriously, here’s the scoop:
- Single-step filters: The easiest filters to use, single-step filters have no options and use no dialog boxes. Just choose the filter from the menu and watch it do its stuff on your image or selection. The basic Blur and Sharpen filters are single-step filters.
- Mini-application filters: Most filters come complete with at least one dialog box, perhaps a few lists, buttons, and check boxes. And almost every mini-app filter has sliders you can use to adjust the intensity of an effect or parameter. These filters are marked in the menus with an ellipsis (series of dots) following their names so that, like other menu commands with those dots, you’ll know that there’s more to come. The controls themselves are easy to master. The tricky part is learning what the various parameters you’re using actually do. How does changing brush size affect your image when using a brush stroke filter? What happens when you select a particular pattern with a texturizing filter? You can read descriptions of how various filter controls affect your image, but your best bet is to simply experiment until you discover the effects and parameters that work best for you. Just be sure that you save a copy of the original image; filters do permanent damage to files — modifying, adding, and deleting pixels.

Most filters include a preview window, but some, particularly those from third-party vendors, may require you to select a Preview option to activate the display. Other filters have an option for previewing the effect in the entire image, rather than just in the filter dialog box’s preview window. That’s because those particular filters use enough computer resources that constant updates take some time. The filter operates more quickly with the full preview turned off. However, if you have a speedy computer and aren’t working with humongous files, the preview delay is probably negligible.