The Select and Mask tool replaces the Select tool and the Refine Edge tool form earlier versions of Photoshop by bringing them together in one tool.
This tool shows up as an option in the top toolbar whenever you make a selection with any selection tool. Click on this to being up the dialogue panel.
Subjects with complex edges, such as a person with a simple body outline and complex hair outline are best masked in two steps, treating the hair and the body separately. See Selecting and Masking Hair.
Top Brush - Quick Selection Tool. Use this inside the image to select the areas you want. Pressing ALT at the same time turns it into a deselect brush to deselect areas you want to remove from a selection. Alternatively click on Select Subject from the top menu bar to use Adobe's artificial intelligence to select the subject automatically.
Middle Brush - Refine Edge Brush. Use the central part of the cursor to paint along the edge you want to detect and refine. A small brush usually works best.
Bottom Brush - Paint Solid Mask Brush. Paint in areas not selected. Works best with a white mask on black.
Lasso Tool - Adds the area selected to the selection, or with ALT pressed deletes it. The Polygonal Lasso tool is also there as a fly-out option.
Hand Tool - Moves the image around.
Magnifying Glass - Magnifies the image, or with ALT pressed makes it smaller.
View Mode - This lets you see your image in different ways using the drop-down selector. Onion skin is often the most useful/ You can cycle through the views by repeatedly pressing the F key. If you are selecting a subject to put onto a new background it can be useful to have the background already there at this stage, as any imperfections show up as they are going to be in the final view. The Transparency slider lets you change how much of the background shows through as the selection is made. - Show Edge - Only works when the Refine Edge Tool is selected and the Radius slider in the Edge Detection section has a value above zero. This shows the edge that Photoshop is trying to detect.
Edge Detection - This controls the level of fine detail extracted in the selection, such as hair. A larger value gives less detail. Ticking Smart Radius will enable the software to choose a thicker or thinner radius where the image calls for this. This is the actual area where Photoshop is analysing the edge using artificial intelligence technology.
Global Refinements - These are much more used for body edge detection rather than hair as they are best for refining smoother edges. - Smooth - This smooths the actual shape of the edge giving smoother curves rather than ragged edges. A small number, such as 2 can help smooth edges. - Feather - This softens the edge by blurring it. A small value, such as 0.5 pixels can help. - Contrast - May need adding back after feathering has been applied as it reduces the grey areas of the mask introduced by feathering. Pushing this to 100% removes all grey pixels restoring sharp edges to the mask. A medium value, such as 50% can help remove some of the blur introduced by feathering. - Shift Edge - Can contract or expand a selection. Shifting the edge inwards can help to remove halos and edge colours. Sometimes medium values of -20% may be needed to remove halos. However fine details is lost e.g. hair, which is better masked separately from the body edge.
PixImperfect says he never uses any of these sliders.
Decontaminate Colours - This helps to remove background colour which shows as a halo around fine detail such as hair. If you have this selected you cannot output to a Selection or a Layer Mask, which are the normal choices for outputting. That is because it works by creating a new layer, expanding the selection just beyond the mask and filling it all with the same colour. This is a destructive process and you have to save this new layer to make it work. There are better ways to do this.
Output - This sets how the result is passed on once you hit OK and it is saved. Saving as a selection or as a mask would be the preferred options of saving the selection you have made. You can go back into Select and Mask from a Layer Mask to further refine the selection.