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Digital Darkroom, Post-Processing & Printing
Sharpen to show--not to kill

Finding a realistic middle ground, by the numbers

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Sharpening photos is easy to overdo—especially for web display. Oversharpened photos seem filled with razor-sharped edges and internal details that look as prickly as a bed of nails. And tiny halos appear on contrasty edges. An oversharpened photo looks unnatural.


For general overall picture sharpening you can avoid most sharpening artifacts by not exceeding these settings:

Size Radius Amount
Web photos 0.4 to 0.8 60 to 100%.
Printed photos (5 x 7 to 8 x 10) 0.8 to 1.5 100 to 150%



Sharpening gone wild: too much sharpening can lead to halos on the edges.

The table at the end of this tip gives more general sharpening guidelines by subject.

More important than such broad recommendations is your approach to sharpening.Let's assume you have a correctly exposed photo that is "sharp" out of the camera—that's to say there is little if any blur from camera or subject movement.

So let's consider four criteria when sharpening:

• The subject
• File size
• Type of output (monitor or print)
• The important content within a picture


Sharpen selectively and subtly for a more natural look.


This selective sharpening looks more natural, doesn't it?

Type of subject

Sharpen soft and gentle subjects less. Some flowers, dreamy landscapes, portraits of babies and often women get minimal or selective (eyes and teeth, maybe hair) sharpening (sometimes you'll even lightly blur parts or all of them). Scenes that may look good with a bit of oversharpening include high action sports like soccer, brightly lit rocky landscapes, close-ups of a butterfly or hummingbird. The point is to customize your sharpening to make it appropriate for your subject and the mood you're conveying.

Size of the file

Large files require more sharpening than small files. Typically you would increase the radius setting as the file size increases. So if you're making a 16 x 20 print, you may set the radius to 2 or 3 and the amount to 200%. If you're making a 4 x 6-inch print, then a radius of 0.8 and an amount of 100% (or slightly less) may serve you better.

The type of output

Monitors have lower resolution than printers. You need to use lower sharpening for monitor/web display than for a print. At the same time, because the monitor's resolution is lower than a print, it's more difficult to determine appropriate image sharpness for a print by looking at the photo on the monitor (where it will look sharper than it does in the print). When you're adjusting an image for print, it should look a bit ovesharpened on the monitor.

The area within a picture

Here's the most important tip. Sharpen important areas within a picture selectively (or blur them selectively). If you've frozen a wake-jumping waverunner in mid-air, you might lightly sharpen the whole picture, but then select the wave runner (use a feather of a pixel or two) and give it extra sharpening—but don't overdo it or it will look pasted into the scene. Similarly, sharpen the butterfly and flower and not the background, in a portrait sharpen the eyes an extra touch. If you variably sharpen several areas in a picture use similar settings so you don't make your technique call attention to itself.

Unsharp mask settings (A=amount, R=radius, T=threshold)
Subject Print Web
General snapshot A-125%, R-1,T-2 A-80%, R-0.7, T-2
Detailed content A-150%, R-1.5, T-1 A-100%, R-0.8, T-1
Action/sports A-175%, R-2, T-0 A-100%, R-0.8, T-0
Female portrait A-80%, R-0.8, T-8 A-40%, R-0.3, T-6
Moody, dreamy content A-60%, R-0.5, T-4 A-60%, R-0.3, T-4

 

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