You can use a quick mask to help you define a difficult selection. To do this, first start a small selection from an image with one of the standard selection tools.

 

 

In the image above, a small selection is started with the rectangular marquee tool. You could just have easily used the lasso tool, the magic wand, or any other selection tool.

 

Once you get your selection started, you can click the quick mask mode button near the bottom of the tool box. This will apply a quick mask over the image..

 

When the mask is applied, you will see what looks like a red overlay on the image. The area that you selected with the selection tool will be white. You will also notice that the foreground and background colours assume the default white and black.

 

Now, you can select a brush tool, or a pencil, and fine tune the selected area by painting on the masked image with the colour white.

 

 

For this image, a paint brush was used to paint white over the gentleman’s collar. You can use several brushes to paint onto the mask, adjusting your tip as required for the level of detail you are trying to achieve. If you make a mistake, you can remove the white by clicking the small curved arrow in the upper right of the toolbox colour squares, to switch the foreground and background colour. When the black and white squares switch, and black becomes the foreground colour, use a brush to paint over the unwanted white area. When you do this, the red overlay will return to the areas you paint. Painting white removes the mask, and painting black adds the mask.

 

For difficult or highly detailed areas, zoom in close on the image, (the Ctrl + = shortcut will zoom in, while Ctrl + - will zoom out), and use a small diameter brush with a hard tip.

 

As you can see, this is a great way to precisely control what regions are exposed (white) in an image.

 

If you want to see what your selection looks like, click the standard mode button (to the left of the quick mask button) in the toolbox.

 

 

 

You will see the animated dashed selection border around the region that you painted white in quick mask mode. While in standard mode, you can do whatever you normally can do with a selection, (i.e. scale it, transform it, fill it etc.) If you want to continue creating your selection, just click the quick mask button again, and the red overlay will return. You can use these two buttons to easily convert from a mask to a selection and back again.

 

Another way to approach the quick mask is to open your image and then click the quick mask button. Next make black your foreground colour, and paint the mask onto your image around the area you want to select.

 

 

Above, a mask is being painted around the eagle. You can use a large brush for large empty areas, and a small brush for detail work. If you accidentally paint the mask over an area you that you want exposed, just switch to a foreground colour of white and paint the mask off.

 

 

Here is the eagle after a mask has been painted around it. To select the eagle, just click the standard mode button in the toolbox. The dashed selection outline will be visible around the region that was left exposed. In standard mode, you can use Layer->New->Layer via Copy, to place the selection on its own layer. Once you do this, you can place and arrange the selection layer over any background you want.

 

 

You can also use a quick mask to paint a mask over a specific part of your image. To do this, click the standard mode button to display your selection, and use Image->Adjustments->Desaturate, or Image ->Adjustments->Brightness/Contrast, or any other adjustment tool from the image menu to modify the selected region only.

 

 

This image above shows a quick mask painted over the lower part of the dune.

 

 

Now, the selected area (exposed area not covered by the mask) has been desaturated by choosing Image->Adjustments->Desaturate in standard mode.