Adobe Photoshop CS5 for Photographers - Martin Evening [135]
Creating a new document
To create a new document in Photoshop with a blank canvas, go to the File menu and choose New… This opens the dialog shown in Figure 5.4, where you can select a preset setting type from the Preset pop-up menu followed by a preset size option from the Size menu. When you choose a preset setting, the resolution adjusts automatically depending on whether it is a preset intended for print or one that's intended for computer screen type work (you can change the default resolution settings for print and screen in the Units & Rulers Photoshop preferences). Alternatively, you can manually enter dimensions and resolution for a new document in the fields below.
Figure 5.4 When you choose File New, this opens a the New document dialog shown here (top left). Initially, you can go to the Preset menu and choose a preset setting such as: Photo, Web or Film & Video. Depending on the choice you make here, this will affect the size options that are available in the Size menu (shown top right). If you use the New document dialog to configure a custom setting, you can click on the Save Preset… button to save this as a New Document Preset (right). When you do this the new document preset will then appear listed in the main preset menu (top left).
Pixel Aspect Ratio
The Pixel Aspect Ratio is there to aid multimedia designers who work with stretched screen video formats. So, if a ‘non-square’ pixel setting is selected, Photoshop creates a scaled document which previews how a normal ‘square’ pixel Photoshop document will actually display on a stretched wide screen. The title bar will add [scaled] to the end of the file name to remind you that you are working in this special preview mode. When you create a non-square pixel document the scaled preview can be switched on or off by selecting the Pixel Aspect Correction item from the View menu.
The Advanced section lets you do extra things like choose a specific profiled color space. After you have entered the custom settings in the New Document dialog these can be saved by clicking on the Save Preset… button. In the New Document Preset dialog shown below, you will notice that there are also some options that will allow you to select which attributes are to be included in a saved preset.
Altering the image size
The image size dimensions and resolution can be adjusted using the Image Size dialog (Figure 5.5). The Image Size dialog normally opens with the Resample Image box checked, which means that as you enter new pixel dimension values, measurement values, or alter the resolution, the overall image size adjusts accordingly. As you alter one set of units you'll see the others adjust simultaneously. When Resample Image is unchecked, the pixel dimensions will be grayed out and any adjustment made to the image will not alter the total pixel dimensions and only affect the relationship between the measurement units and the resolution. Remember the rule I mentioned earlier: the number of pixels = physical dimension × (ppi) resolution. You can put that to test here and use the Image Size dialog as a training tool to better understand the relationship between the number of pixels, the physical image dimensions and resolution. The Constrain Proportions checkbox links the horizontal and vertical dimensions, so that any adjustment is automatically scaled to both axis. Only uncheck this box if you wish to squash or stretch the image when adjusting the image size.
Figure 5.5 To change the image output dimensions while keeping the resolution locked, leave the Resample Image box checked. To change the image output dimensions so that the resolution auto-adjusts to the new image dimensions, leave the Resample Image box unchecked. Click on the Auto… button to open the Auto Resolution dialog shown here. This can help you pick the