Wednesday, November 18, 2009

Photoshop - sharpening tools tutorial

Photoshop comes with too many ways to sharpen a photo. It gets to be confusing. You have
  • sharpen
  • sharpen edges
  • sharpen more
  • smart sharpen
  • unsharp mask
Sharpen and sharpen more seems to just add more noise to my photographs.
Let's focus on the one I use almost exclusively.
My favortie is unsharp mask. It seems to be the most useful sharpening tool.The Unsharp Mask searches through your image looking for where colors change, and sharpens those areas. The Unsharp Mask is superior to any other sharpening because it makes decisions based on adjacent pixels, not random color changes, so it usually can find and sharpen just the true edges of color areas
It is the it creates a halo around high contrast area to emphasize edges.
Let's take a look at what the radius setting does.
In my example you can see that the more I increase the Radius the more it adds both a white edge and black edge to areas of contrast.

The amount changes the amount of contrast between pixels. The more the amount the more you will notice a change in the picture. If you set this too high then the halos around edges will be too noticeable and the picture will look terrible. The amount that you need is determined by the subject matter and the resolution of the image. If the subject matter contains something like trees or people then I’ve noticed that a lower amount is fine. For buildings and objects with sharp edges, a higher amount works. For high resolution images you’ll need to increase the amount more. You’ll need to experiment with it.

The Radius is the size of the halo around the edges. One side of the edge will have a lighter color and the other side of the edge will have a darker color. The number that you are changing is the number of pixels surrounding the high contrasting areas. High resolution images will need a higher radius. Low resolution images will need a lower radius. Also I’ve noticed that the radius and amount can be inversely proportional, meaning that higher radius can have a lower amount and a lower amount can have a higher radius. Once again, you’ll have to experiment.

Finally, the Threshold determines what exactly you want an edge to be. Photoshop thinks that colors that are touching and are very different from each other are edges. If your threshold is set to 0 then everything will get sharpened (including noise). This option allows you to choose what should get sharpened. A threshold of over zero will only sharpen areas with high contrast and won’t touch areas with low contrast. This is helpful because you don’t want stuff like noise getting sharpened along with real edges. The higher the setting the less areas the sharpening will be applied to.

Images can easily be over-sharpened. When you take it too far, a "ghosting" begins to appear around the edges, detracting from the overall appearance. Be careful not to over sharpen your images.

In no time at all, you'll be sharpening images perfectly.

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