Section 3: Selections and Masks

Selection tools in Photoshop enable us to isolate certain parts of an image and adjust, modify and transform it. Something that the Marquee, Lasso and Magic Wand tools all have in common is the add/subtract/intersect option. This can be found in the options bar.   

• Marquee Tools
• Lasso Tools
• Magic Wand Tools
• Transforming Selections
• Quiz

Selection tools enable us to isolate certain parts of an image and adjust, modify and transform it. Something that the Marquee, Lasso and Magic Wand tools all have in common is the add/subtract/intersect option. This can be found in the options bar.   

In addition to making a basic selection, this option enables us to add, subtract or intersect with a current selection. Let’s take a look at the selection tools and then complete an exercise to try out the different options.

Marquee Tools  

The marquee tools enable us to make selections in an image using either a rectangular or elliptical shape, using a click and drag action. By default the selection starts at the point where we click on the image and grows in the direction we drag it. If we press Alt/Option and then click and drag, the selection grows from the centre outwards.

Like with all the other tools in the Toolbox, there are additional options available in the Options Bar. We have already looked at the add/subtract/intersect option. We can also change the edge feather and the selection style.

 

By changing the value of the feather, the edges of the selection is softened. We can also change the style of the selection, selecting either a freeform, fixed aspect ratio or fixed size area.

    Exercise 3.1

To practice the use of the Marquee tool we will create an old style headshot.

1. Open the image named S3E1.jpg from the CD.
2. Select the Ellipse Marquee tool from the Toolbox.
3. To soften the edges of the selection, change the feather, in the options bar to 20px.
4. Placing the tool tip in the centre of the woman’s face, press Alt/Option and drag the Marquee to form an elliptical selection slightly larger than the face. To adjust the position of the selection, click inside it and drag it to the desired position. If you make a mistake, simply click outside the selection and try again.
5. We are now going to copy the selection to a new document. Go to the Edit menu and select Copy or use the keyboard shortcut Ctrl + C / Cmd +C
6. To create a new document to paste our image into, click the File menu and select New or use the keyboard shortcut Ctrl + N / Cmd +N. The settings in the dialog box that follows have automatically been populated with the size of the selection that we copied. To change the size of the new document, enter the new size now and click OK.  
7. With the new document open, paste the copied selection either by clicking on the Edit menu and selecting paste or using the keyboard shortcut Ctrl + V / Cmd +V.
8. Our selection was pasted to a new layer (more on this later) so we need to flatten the image before saving it. To do this select Flatten Image from the Layers menu.

Lasso Tools    

The Lasso tool enables us to draw our selection. This can be very useful, but it is quite difficult to draw an accurate selection. The Lasso tool has three variations: Freeform Lasso, Polygon Lasso and Magnetic lasso.

The Freeform Lasso draws a selection wherever the tool is moved on the image and automatically closes the selection when the mouse button is released.

The polygon Lasso draws a selection with straight lines, automatically closing the selection when the mouse button is double clicked.

The Magnetic Lasso draws a selection on the closest high contrast point near the tool tip. I.e. when the image is a black circle on a white background, the Magnetic Lasso will stick to the edge of the black circle because of the contrast between the black and white.

When one of the Lasso tools is selected, we can again find some additional option in the options bar.  

 

The first one is the Feather option which, similar to the Marquee tools, softens the edges of the selection by blurring the outer pixels. The Anti Alias option softens the edges of a selection by reducing the colour contrast between edge pixels.

    Exercise 3.2

To practice the    use of the Lasso tools we will select an object and remove its background.

1. Open the image named S3E2.jpg from the CD.
2. Select the Polygon Lasso tool from the Toolbox. Make sure the feather is set to 0px in the Options Bar.
3. Start anywhere on the outside edge of the yellow chair and trace the outline, until you reach the point where you started. When you see a little circle next to the tool tip, this means the selection will be closed.
4. If we copy the chair now we will still be left with the blue sections under the armrest. To prevent these areas being copied, we need to subtract them from the current selection. To do this set the Lasso option in the options bar to ‘subtract from selection’.  A little minus appears next to tool tip. Now select the blue areas under each armrest and the little strips between the backrest. We can see that the original selection stays in tact.
5. We now have only the yellow chair selected, but since we want to remove the background, we have to invert the selection. Simply click the Select menu and select Inverse or use the keyboard shortcut Ctrl + Shift + I / Cmd + Shift + C. We now have the entire background selected.
6. To clear the background, go to the Edit menu and select Clear. We are left with only the yellow chair on a clear background.

Try this exercise using the Freeform and Magnetic lasso tools too. It will give you a good idea of when to use each one.  

Magic Wand Tool

The Magic Wand tool makes it easy to select a complex area with a single mouse click. It samples the area that is clicked and selects all adjacent pixels with a similar colour value. How closely the selected area matches the original colour depends on the tolerance that is set in the options bar.

Exercise 3.3

To practice the use of the Magic Wand tool, let’s select an area in an image.

1. Open the image named S3E3.jpg from the CD.
2. Select the Magic Wand tool from the Toolbox.
3. Check that the tolerance is set to 30 in the options bar.
4. Click on the blue letter A to create a selection around it. If the whole letter is not selected with one click, set the Magic Wand option in the options bar to ‘add to selection’ and continue.
5. Once selected, the selected area can now be moved, copied or transformed in any way necessary.

Transforming Selections

Once we have made a selection, we might want to change it. There are several tools to do this and they are found in the Select Menu. From here we can transform selections in various ways. By selecting the Transform Selection item from the menu, it is possible to change the shape of a selection using the standard transform options: scale, rotate, skew, distort and perspective.

When clicking on modify, in the select menu, we are presented with four additional options: Border, smooth, expand & contract. With these it is possible to change the selection more precisely.

 

 Border                Smooth                Expand             Contract

Border will render a border selection around the currently selected area. The width can be specified in the dialog box that follows and is measured in pixels.

Smooth will remove any jagged edges from the selection. In the dialog box that follows, we can specify what radius from the edge this change will affect.  

Expand will enlarge the selection with a specified number of pixels.

Contract will shrink the selection with a specified number of pixels.  

 

Section 3 Quiz

1. What option does the Marquee, Lasso and Magic Wand tools all have in common?
2. Which setting softens the edges of a selection?
3. Which tool selects pixels with similar colour values?