In a vector drawing environment, selecting elements is a breeze: you just get the pointer tool, click on an object and it’s selected. Selecting pixels in a bitmapped image, on the other hand, can be a tricky business. That’s why Photoshop offers so many ways of making selections. The program offers selection tools, modifier icons and keyboard modifiers too.

Sometimes, selections take just a couple of minutes; others may take you an hour. Whenever I run Adobe Photoshop courses, I always give students plenty of practice on making selections, so that they start to get familiar with the often “fiddly” techniques involved.

If you’ve just spent a fair amount of time making a selection, the last thing you want is to have to repeat the tricky business of making the same selection again in the future. Naturally, you will want to preserve the selection and be able to reinstate it at some point in the future. Luckily Photoshop offers a couple of different ways of doing this. You can save a selection as a path or as an alpha channel.

To preserve a selection as a path, choose Make Work Path from the Paths panel menu. Photoshop will then ask you to enter a number representing the tolerance setting that the program should use in creating the vector path. The best results are normally obtained with a value somewhere between 1 and 2; although the full range of permitted values is from 0.5 to 10.

Photoshop contains a number of tools which Illustrator users will instantly recognise as path manipulation tools. The pen series of tools is used for creating vector paths as well as adding and deleting points. The direct selection tool is used for selecting and manipulating points on a path. Using these tools, it is possible to create a path which very closely follows a subject or area within an image that we wish to select.

A path is not quite the same thing as a selection, paths can be converted into selections at any time. Simply highlight the path in the Paths panel and choose Make Selection from the Paths panel menu.

To save a selection as an alpha channel, choose Save Selection from the Select menu. When you save a selection in this way, Photoshop creates an alpha channel which is simply a special type of channel that can be viewed by going to the Channel window and clicking on its name. The colour channels within an image show the strength of each primary colour in different parts of an image. Alpha channels, by contrast, are greyscale images which use a visual code to represent selections and masks. Dark areas represent masked areas and white areas represent those areas which will become highlighted when the channel is loaded as a selection.

The different levels of greyscale information inside the alpha channel represent different levels of selection, making alpha channels ideal for saving selections with feathers and fades. Paths, by contrast, are incapable of representing different degrees of masking and selection. Paths are really vector shapes, superimposed on the bitmapped image, which can be manipulated using a series of tools imported from Illustrator, Adobe’s vector-based drawing program.

The author offers Adobe Photoshop CS4 tuition in London and the UK. Telephone 0800 1950 502.

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