1.

To begin, start Photoshop CS, and use the file browser to open the Palm Tree image.

When your image is open, close (X) the file browser.

2.

Next, begin a selection by choosing the Lasso tool from the tool box.

Once you select the lasso tool, draw a rough selection outline around the palm tree.

3.

It will be very difficult to completely isolate the palm tree using standard selection tools. This looks like a situation where a quick mask could help.

Click the Quick mask button in the toolbox to turn your selection into a quick mask.

Press the Ctrl + = shortcut to zoom in for the fine detail. Use a small paint brush (< 10 pixels) to paint with a black foreground colour over the image.

Here the image is zoomed to 600%, and a paint brush of 1 pixel diameter is being used to isolate the palm tree on an almost pixel by pixel basis.

This is a rather painstaking procedure, and the extraction tool (click Filter then Extract) might do a better job. Using the extraction tool, you would just highlight the edges of the palm tree, and the selection would be automatically made based on contrast. The results may or may not be better than the quick mask method.

For the purposes of this exercise, we will continue with the quick mask method.

Here is a zoomed out view of the current progress.

It looks like this selection may take a long time to complete!

4.

If you look at the channels palette for this image, you will see that a quick mask alpha channel has been stored in the bottom of the channels list.

The next step is to save the image, and the quick mask channel with it.

5.

From the menu bar, click File and then click Save As.

In the save as box, save your image as Practice14 in your practice folder. Make sure you save the image under TIFF format, and also make sure that the Alpha Channels checkbox has a mark in it. When you are ready, click the Save button.

6.

When the TIFF options box appears, select the byte order that is appropriate for the type of system you use.

Don’t worry about image compression or image pyramid settings.

When you are ready, click OK.

7.

Close (X) the palm tree image. Your Photoshop CS screen should now be empty.

8.

Click File from the menu bar, and then click Practice14.tif from the Open Recent sub menu.

9.

The image you were working on should appear on your Photoshop screen, with the quick mask channel intact as you left it.

Perform some more adjustments to the quick mask to further refine your selection. Click the standard mode button in the toolbox to view your selection outline.

10.

You have successfully created and saved a quick mask/selection as an alpha channel.

Next, save your image again as a TIFF format to preserve the alpha channel information.

11.

Close (X) Photoshop CS