The Retina display on the new iPhone 4 is terrific – it really makes a difference when watching videos and photo slideshows. The iPhone’s camera has been improved too, providing 5-megapixel resolution for still photos and HD 720p resolution for video recording. That combination makes the iPhone 4 ideal for shooting and viewing short video clips.

The iPhone 4 already has the ability to trim video clips before you send them to friends or upload them to YouTube but the new iMovie for iPhone lets you do much more.

We wouldn’t suggest that you edit a full-length movie with it – the transitions and titling tools are too limited for that – but at just £2.99 it’s perfect for quickly putting together some short clips that you can share.

1. On side  When you launch iMovie it displays a blank workspace, with just a prompt telling you how to start a new editing project. You can use iMovie with the iPhone either upright or on its side, but it works best when turned sideways as you get to use the full area of the screen for editing.

2. Theme Music  Tap the ‘+’ button to start a new project. The next step is to select a theme that adds graphics and titles to the project. Each theme also has its own optional soundtrack that you can turn on or off. We’ll select the Travel theme for now, but you can change the theme later if you want.

3. Quick clips  Tap the Insert button and you’re taken to the media browser window, which allows you to select any photo or video clip that you’ve got stored on your iPhone. You can also select any song stored on the iPhone, and use it as your soundtrack. You can shoot live video and insert it straight into iMovie too.

4. Editing mode  Tap on a clip and it’s automatically inserted into the timeline on the bottom of the editing window. Above the timeline is the main preview window where you can play and preview your project to see how it looks. The red playback cursor sits at the end of the clip – which is marked as being 24 seconds long.