Today’s Question: When using the Quick Selection tool [in Photoshop], is there a way to change how wide of colors the brush recognizes?
Tim’s Quick Answer: No, the Quick Selection tool does not include a setting such as the Tolerance control for the Magic Wand tool. However, you can improve your results by setting the right brush size with a hard-edged brush, and by using the “add” and “subtract” options to refine the selection.
More Detail: The Quick Selection tool is something of a more intelligent version of the Magic Wand tool for creating selections in Photoshop. The Magic Wand tool uses a simple range of values based on the area you sample and the current setting for Tolerance. Pixel values are evaluated strictly based on whether the tonal value for a pixel on each channel (red, green, and blue typically) is within the defined range compared to the sample value.
The Quick Selection tool uses a similar approach of sampling the image, but in a more sophisticated way. In effect, the Quick Selection tool is attempting to find the edge of the area you’re trying to select, based on painting in the image to define the color and tonal values for the area you’re attempting to select.
You can help improve the accuracy of the sampling with the Quick Selection tool by using a small enough brush to make sure you don’t paint into areas beyond the area you’re trying to select. In addition, I recommend setting the Hardness value on the brush popup on the Options bar to 100%. This will help you be more precise with the Quick Selection tool, especially when you’re painting close to the edge of the area you are trying to select.
To help improve the quality of the selection edge, you can use the Add and Subtract options. The Quick Selection tool switches to the Add option after the first time you paint with the tool, but I am still in the habit of holding the Shift key on the keyboard to access the Add feature, since that is the same keyboard shortcut used by the other selection tools. With the Add feature enabled, you can paint over additional parts of the area of the image you want to select to sample those additional areas.
If an area you don’t want included in the selection becomes selected, you can choose the Subtract option from the Options bar, or hold the Alt key on Windows or the Option key on Macintosh while painting over the area of the image you want to subtract from the selection.
While it can be helpful to have a selection that is absolutely perfect, keep in mind that if you are going to be using that selection as the basis of a layer mask for a targeted adjustment or composite image, you can always refine that layer mask later in your workflow, which is often easier than trying to fine-tune a selection.