Sharpening with the Unsharp Mask.
So the first thing you should do is forget about the menu
options Sharpen, Sharpen More and Sharpen Edges. These are
merely default settings of the Unsharp Mask. The Unsharp
mask can do these things and a whole lot more.
But what is Unsharp masking? Wikipedia says...
masking is an image manipulation technique now familiar to
many users of digital image processing software, but it
seems to have been first used in Germany in the 1930s as a
way of increasing the acutance, or apparent sharpness, of
photographic images. The "unsharp" of the name derives from
the fact that the technique uses a blurred, or "unsharp",
positive to create a "mask" of the original image. The
unsharped mask is then combined with the negative, creating
the illusion that the resulting image is sharper than the
Digital Unsharp masking is a little different.
First, it increases contrast at the pixel level making dark
pixels darker and light pixels lighter.
Second, it accentuates lines by searching for broader areas
where light and dark tones meet and making the dark edges
darker and light edges lighter.
A point to remember: Sharpening only makes
the image "look" sharper. No amount of sharpening will fix
motion blur. Sharpening cannot fix a significant lack of
Also, sharpening should be done as a last step in your
digital workflow, this is my opinion and seems to be shared
by most of the digital imaging community.
So how do we go about using the Unsharp Mask tool in
1. The first thing we should do is view the image at 100%
of the output resolution.
2. Select the area of your image you wish sharpened, or
don't select anything to apply the mask to the entire
image. Which one you choose will depend on your image and
the results you want. If you select a part of the image, I
suggest you use the 'Feather' feature from the 'Select'
menu to reduce any harsh lines that may be created between
your selection and the rest of the image.
3. Start the Unsharp Mask Filter by selecting the Filter
menu, Sharpen and Unsharp Mask. The Unsharp Mask filter has
Amount: Controls the intensity of the
effect (not the actual effect)
Radius: Is the effect. This controls the
way edges are treated, how much halo effect is applied. Too
much and you will lose subtle detail or your image will
Threshold: suppresses noise in smooth
areas. The levels refer to the number of levels that need
to be different for the effect to be applied. Too few, and
you might have noise in your image, too many and you may
suppress the sharpening effect entirely.
4. Reset the Amount, Radius, and Threshold to their lowest
values (0, 0.1, 0) as below
5. The settings you use will be different for each image
but after playing with the settings you will find a
combination that should work with most of the images you
take, with a little adjustment.
a) Start by moving the Amount slider to it's maximum
b) Now set the Radius. Be very precise, but err on the side
of a little more. Especially if you're going to print your
image on an inkjet printer.
c) Now set the Threshold, but only if necessary. If noise
is visible, or too high adjust the Threshold until the
noise is at your desired level. When done, click OK.
d) Finally, fade the effect of the Unsharp mask to
luminosity. This limits the effect to just light and dark
areas without effecting colour. From the Edit menu select
'Fade Unsharp Mask' and select Luminosity from the 'Mode'
menu. Adjust the 'Opacity' until you have a pleasing
You're done. Don't forget to save your image.
Remember: If you're printing your image on
an inkjet printer, be slightly aggressive with the Radius
setting. This will counter the bleed that occurs as ink is
absorbed by the paper. If you're outputting your image for
the screen, be very precise.
Now that you know how to use the Unsharp Mask Filter, don't
ever use the other options, they're a waste of time... in
PS. Digital noise is sometimes much more evident in the
Blue colour channel. You can check this by selecting the
Channels Palette and then highlighting the Blue channel.
Compare this with the Red and Green channels. If the noise
is much higher, consider applying a slight blur to this
channel only, and/or sharpening only the Red and Green
channels. A simple way to do this is to apply a test
sharpen to the RGB channel, take a note of the settings and
apply half of the amounts to both the Red and the Green
PPS. My example image is over sharpened to show the effect.