Digital Darkroom Questions (DDQ)July 29, 2008
by Tim Grey www.timgrey.comtim@timgrey.com
Books: www.timgrey.com/books/index.htmBlog: www.timgrey.com/blog
Question: Is it true that you need to change settings for the Eyedropper tool in order to get the best results for the Magic Wand selection tool? A friend of mine told me this, but it doesn't make sense to me.
Yes, it is indeed true.
Specifically, the Sample Size setting on the Options bar for the Eyedropper tool affects the behavior of the Magic Wand tool. I'm not sure why Adobe has never just put the same control (or a different control with the same option) on the Options bar for the Magic Wand tool, but they haven't.
The Sample Size setting determines how large an area will be averaged together when taking a measurement with the Eyedropper tool, or when sampling an area to define a selection with the Magic Wand tool. The default is Point Sample, which can be a problem for the Magic Wand tool because you might inadvertently click on a pixel with a random value that doesn't really match the surroundings (such as a dust spot in the sky that is too small to see). I generally use the "3 by 3 Average" or "5 by 5 Average" setting, because it helps to average out any random pixel variations, producing more accurate results.
In some cases you might even want to increase the value significantly, perhaps even up to the maximum setting of "101 by 101 Average". This will obviously average a relatively large area of the image compared to the single pixel you actually clicked on, but this can be a great solution when trying to create a selection with the Magic Wand tool in an area that has a somewhat significant amount of variation in terms of tonality, but still has good separation from the area you're trying to avoid selecting.
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