Chap35

DIGITAL MEDIA FUNDAMENTALS

Image Enhancement using Filter.


In This Chapter, you’ll learn on: Define what is filters and its main applications


What are filters? Filters are processes that are used to change the

appearance of an image, layer, channel or selection in image editing software. You can use filters to clean up or retouch your photos, apply special art effects that give your image the appearance of a sketch or impressionistic painting, or create unique transformations using distortions and lighting effects. Filters also called plug-ins because you can install or uninstall it independently.


How Filters work All filters do one simple thing in a seemingly

complicated way. Applying a filter is basically same as giving 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 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).


Filters got their name from the world of photography, where you could change how a picture looked by placing a filter over the lens. The changes can make your photos brighter, redder or fuzzier. Image enhancement filters can do the same thing, just with much more variety and control. Most photo editing program comes with a lot of built-in effects that can make your image look like everything from a painting to a bad photocopy.

Original Image Image with Motion Blur filter


Types of filters Photoshop have more than 14 category and 110

different filters that do many different things. We can classify filters into two basic categories, corrective and destructive.

All corrective and destructive filters are single-step or Dialog box-based filters.


Corrective filters: Corrective filters are usually used to correct or fix

problems that you have with the image. They fine-tune color, add blur, improve sharpness, or remove such nastiness as dust and scratches.

Although corrective plug-ins can be fairly destructive to certain pixels, they don’t change the basic look of an image in general. You might not even notice that a corrective filter has been applied unless you compare the new version of the image with the original. In corrective filters, pixels are modified, but the basic appearance of the image remains the same, albeit hopefully improved.


Some examples of corrective filters areo Averageo Blur Filters e.g. Gaussian Blur, Lens Blur,

Motion Blur, Radial Blur, Smart Blur: o Sharpen Filters e.g. Sharpen Edges, Sharpen

More, Un-sharp Mask


Destructive filters Destructive filters tend to obliterate at least

some of an image’s original detail (some to a greater extent than others) while they add special effects.

They may overlay an image with an interesting texture, move pixels around to create brush strokes, or distort an image with twists, waves, or zigzags.

You can often tell at a glance that a destructive filter has been applied to an image. In destructive filters, pixels are also modified, but the image will usually look very different from its original.


Destructive filters

Filters range in variety from the corrective (Left), to the destructive (right).


Single-step filters The easiest filters to use, single-step filters have no

options and use no dialog boxes. Just select 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.

Dialog box-based filters These filters utilize preview windows, buttons, slider controls,

and menus to distort, pixelate, sharpen, stylize, apply textures, and perform other functions. Most filters come complete with at least one dialog box, along with (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 (a series of dots) following their names; like with other menu commands that show those dots, it’s an indication that you’re about to be presented with a dialog box where more options are lurking. Dialog box-based filters act almost like mini-applications.

Example of a dialog box


Smart Filters The Filter menu also provides an opportunity to convert for

Smart Filters. If you convert your layer to a Smart Object, you can then apply a Smart Filter. A Smart Filter is smart because it doesn’t alter your image pixels, but merely hovers above them, thereby allowing you to re-edit, or even remove, the filter if necessary.

Technically, the filters are applied to your pixel data, but

Photoshop always retains the original pixel data inside the Smart Object. Then, each time a filter is edited; Photoshop installs the original pixel data and reapplies the filter. Smart Filters act like layer effects, appending themselves to your layer, where they can be edited, rearranged, and deleted at any time.

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Chap35