When I first started using Photoshop I thought I could make an out of focus or blurred image look like it was in focus. Photoshop can not do this. I tried so hard I created what I now come to call halos in my images. Photoshop works its magic; by giving the illusion the image is sharper than it really is. Photoshop does this is by looking for edges where dark tones are adjacent to light tones.
The magic is created by taking some of the dark and light pixels, and making them darker and lighter than they were when you started out.
Lets look at this image and see what happens when we apply the Unsharp Mask in Photoshop.
We see at 1600% when the Unsharp Filter is applied, Photoshop has made all the pixels adjacent to its contrasting neighbor, both darker and lighter.
Now, if we increase the sharpening amount, what we are effectively doing is just increasing the contrast between the lighter and darker pixels. While looking in the preview window we begin to notice a white line begin to appear between the contrasting edges of tones in our image.
This is what is known as a Halo and this is not a good thing despite what your religious beliefs are. Our goal as photographers is to make that halo just strong enough to give the illusion of a sharp edge, without making the Halo itself visible in the image.
Amount controls the strength, and the Radius controls the width of the Halo.
1. I advocate sharpening only at the very end of your work flow. Correct your color, adjust your tones, and do all your retouching.
2. Save your image as a master image.
3. Resize a copy your image to the desired size for the output that you want.
4. Then, and ONLY then sharpen your image.
These are general principals to keep in mind when sharpening an image.
In my Part II of this tutorial, where going to apply these principals to some real photographs using the Unsharp Filter, and the Smart Sharpen Filter.
Visit my forum for more Photoshop tutorials for all of us photographers. http://www.microstockpix.com/smf/
See you next time. The MIZ
(c) 2006 Robert Mizerek [contact] [bio ]
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