Photoshop Filters You Really Need
Photoshop has several filters that you can use on just about any image to improve or finesse it. Most photos, for example, benefit from at least a little bit of sharpening to improve the detail in the image.
In some cases, you want to decrease the visible detail in an image in some areas to hide defects, or perhaps you want to blur a background to draw more attention to the subject of your shot. And Photoshop has a couple of filters that you’ll find handy for correcting lens distortion and reducing noise (specks of red, green, and blue) in digital photos.
Some filters aren’t available for images in 16-bit color and some aren’t available when you’re working in CMYK (cyan/magenta/yellow/black) color mode. Almost all of the filters are available for 8-bit RGB and grayscale images. (No filters are available for GIF or PNG-8 images, which use Indexed Color mode.)
And keep in mind that you can apply filters to specific areas of an image by making a selection first. If you need to use a filter and it’s grayed out, choose Image→Mode and convert to 8-bit/channel RGB mode.
You can instantly reapply the last-used filter exactly as it was applied with the keyboard shortcut Cmd+F (Mac)/Ctrl+F (Windows). If you’d like to reopen that last-used filter’s dialog box to change settings before reapplying, press Option+Cmd+F/Alt+Ctrl+F.
Sharpening to focus the eye
When looking at an image, your eye is naturally drawn to certain areas first. You generally look at bright areas before dark areas and areas of detail before smoother areas in the image. Compare, for example, the three photos in this figure (which were taken using different focal lengths and lens apertures).
Using Photoshop’s various sharpen and blur filters enables you to control the amount of detail throughout your image or, when working with selections, in specific areas in order to control the areas to which you want to draw attention.
Photoshop offers six sharpen filters, three of which you can ignore. The Sharpen, Sharpen More, and Sharpen Edges filters have no user-definable settings and simply work in accordance with their names. Sure, they do a reasonably good job, but you don’t have that all-important control over your images! Skip them in favor of the they-take-some-work-but-they’re-worth-it sharpening filters: Unsharp Mask, Smart Sharpen, and the new Shake Reduction filter.
The Unsharp Mask filter is, indeed, a sharpening filter, despite the name (which comes from the blurry — unsharp — mask created from a copy of the image and used in the sharpening). As you can see in the figure, Unsharp Mask offers three sliders to adjust the appearance of your image.
In the upper left, you see the original image at 100% zoom. The middle image shows the sharpening at 100% zoom. To the right is a 300% zoom in the preview area of Unsharp Mask’s dialog box.
The Smart Sharpen filter itself isn’t new, but how it works has been greatly improved. It provides you with an incredible amount of control over the sharpening process. Although it won’t (quite) be able to give you a crisp image of that bank robber from the pixelated, blurry surveillance camera (so far, that happens only on TV), it will help you improve just about any image.
Those who photograph through microscopes and telescopes might find this filter particularly useful. However, remember that although you might improve an image, some blurs simply won’t be removed by sharpening.
This figure shows how well Smart Sharpen works with an appropriate image. (Note that the Preview check box is deselected in order to show the unsharpened original to the right.) In this image, the blurring is consistent throughout the subject of the shot, and there is a reasonable amount of blur.
In the figure, you can see that when you click the arrow to expand the Shadows/Highlights, all three sections of sliders are available. The Reduce Noise option doesn’t reduce noise (as would the Noise Reduction filter), but rather reduces the amount of sharpening applied to existing noise so that it doesn’t become more prominent.
Fading the filter in the shadows also helps keep digital noise less visible. Reducing the amount of sharpening in the highlights can prevent unwanted attention being drawn to small bright areas within the image.
When working with Smart Sharpen, try dragging the Amount slider to perhaps 250%. Then drag the Radius slider to the right until you start seeing halos along distinct edges. Back off the Radius slider a bit to reduce the halos, and then bring the Amount slider down to a more reasonable level, to an amount that provides the appropriate sharpening for the image content.
And if you liked the older version of Smart Sharpen, click the gear button in the upper-right and select Use Legacy from the menu that appears.
New to Photoshop is the Shake Reduction filter. If you shot at a slightly too-slow shutter speed (or during a minor earthquake), the image may have some blurring because the camera itself moved a bit while the shutter was open. This is most apparent when shooting at the longer focal lengths of zoom lenses.
The Shake Reduction filter analyzes the image, selects what it thinks is a representative area of image upon which to base the amount of shake reduction, and then generates a preview. You adjust the sliders (and can change the setting in the Source Noise menu from Auto to Low, Medium, or High).
The “detail loupe” window (in the lower-right corner of the figure) enables you to zoom in on an area of the image while making adjustments. Click the second button from the right at the bottom to undock the loupe and you can drag it anywhere in the image, or click in the image window to have the loupe re-center on that point.
You can also click the Close button in the upper-left corner to dock the detail in the lower-right corner of the Shake Reduction dialog box. To zoom in on the image itself, Command/Ctrl+click. To zoom out, Option/Alt+click.