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smittyswebworxs
Participant
January 29, 2018
Answered

Magic Wand tool tolerance setting

  • January 29, 2018
  • 1 reply
  • 20192 views

I have looked all over the net and can't seem to find a definitive answer to the tolerance setting for the magic wand tool.

Let me explain:

Say I have the magic wand tool active and set the tolerance to 20.  Now when I click in the image i get a selection pattern based upon that tolerance setting.  And I know that the higher the tolerance setting, generally, the larger the resulting selection.  I also understand how the "contiguous" and "sample all layers" check boxes affect the resulting selection. What I am wanting to know is this:  exactly how does the tolerance setting affect the selection.

For example, again, let's say I have a tolerance setting of 20 and when I click on the image I click on a pixel that has the color #efb7b6.  How does Photoshop use the tolerance setting to determine what other pixels become part of the selection.  Does Photoshop then select all colors that are within 20 points of each of the Red, Blue, and Green portions of that color.  For example, do colors FFb7b6, efCBb6, and efb7CA get selected because they are within 20 points of the base color  but colors efCCb6, and dfb7CB don't get selected because they are not within 20 points of the base color.

What's the deal on the tolerance setting for the magic wand tool???

Thanks,

Warren

This topic has been closed for replies.
Correct answer Terri Stevens

The whole thing just makes more sense when talking RGB values instead of hex. Not right or wrong... When working with images you want to use the RGB values. You slowly train yourself to see color casts in the numbers. Over time RGB will be very valuable to you.


I would say HSL is probably even more useful than RGB for understanding the magic wand tolerance. This is because by tolerance Adobe is really talking about luminance or how bright a pixel is. A tolerance of 20 means that when you click on a pixel with the 'sample size' set as 'point sample' then all contiguous pixels with a luminance of +20 through to -20 of the pixel you clicked on will be selected, with the luminance being calculated as the average luminance of the red, green and blue channels for that pixel. This is why the maximum tolerance can only be set to 255 as 8 bit images have 256 greyscale luminance levels. It's unwise to use hex colors as they are color model dependent.

1 reply

c.pfaffenbichler
Community Expert
c.pfaffenbichlerCommunity Expert
Community Expert
January 29, 2018

If you stop bothering with that manner of numbering colors and use proper RGB values it may appear clearer.

Quote from the Reference:

Tolerance Determines the color range of selected pixels. Enter a value in pixels, ranging from 0 to 255. A low value selects the few colors very similar to the pixel you click. A higher value selects a broader range of colors.

T
teachbit
Participating Frequently
January 29, 2018

GEM IN THE ROUGH: CHANGING THE MAGIC WAND'S SAMPLE SIZE

Did you know you can change the way the Magic Wand calculates which pixels to select? Of course, you didn't; that's because the setting that controls the Magic Wand's selections appears only when you have the Eyedropper tool selected. (Makes perfect sense, doesn't it?) You can read about the Eyedropper tool on The Eyedropper Tool, but here's what you need to know about it to tweak the Magic Wand:

Over in the Tools panel, select the Eyedropper tool (its icon, not surprisingly, looks like an eyedropper; it lives beneath the Crop tool). When you do that, a Sample Size pop-up menu containing a slew of settings appears in the Options bar.

From the factory, the Sample Size menu is set to Point Sample, which makes the Magic Wand look only at the color of the pixel you clicked when determining its selection. However, the menu's other options cause it to look at the original pixel and average it with the colors of surrounding pixels.

Depending on which option you choose, you can make the Magic Wand average the pixel you clicked plus the eight surrounding pixels (by choosing "3 by 3 Average") or as much as the surrounding 10,200 pixels (by choosing "101 by 101 Average"). The "3 by 3 Average" setting works well for most images. If you need to select a really big area, you can experiment with one of the higher settings like "31 by 31 Average".

After you make your selection, simply activate the Magic Wand and then click somewhere in your image to see the effect of the new setting. It's that simple.

Quoted from: Photoshop CS5: The Missing Manual [Book]

    J
    Jacky36245771gkcu
    Participant
    March 22, 2024

    nope it doesn't work for me. i still cannot make individual selections even after i changed the settings in eyedropper

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