Section 2: Working with Documents

Let’s start by opening our first document. Remember what I said in the beginning about there being many ways to do the same thing? Here is our first example of this. Let’s start with the most obvious way and then go from there.

• Opening a Document
• Navigator, Hand & Zoom
• Duplicate
• Image Size & Resolution Primer
• Canvas Size
• Crop Tool
• Image Modes
• Saving Images
• Quiz

Open a document

Let’s start by opening our first document. Remember what I said in the beginning about there being many ways to do the same thing? Here is our first example of this. Let’s start with the most obvious way and then go from there.

Go to the File menu and click Open Image. In the dialog box navigate to the samples folder on the CD and select S2_Lighthouse.jpg. Click open.

Now that we have opened our document, let’s start working on it.

Navigator, Hand & Zoom

After we open an image in Photoshop, we can change the way our document is displayed by using one of the following tools or shortcuts:

The navigator palette can be found on the right hand side of the screen. If it is not visible, go to the Window menu and click on Navigator to show/hide it. We can see a thumbnail of our image surrounded by a red square. Everything inside the red square is visible in the document window. Use the slider below the thumbnail to zoom in and out of your image. Note how the size of the red outline changes and corresponds to the view in the document window.

On either side of the slider there is a button that enables you to zoom in or out in set increments with a simple mouse click. To the left of the slider the magnification is shown. By changing the percentage in the navigator we can zoom in or out very accurately.

Yet another way of zooming in or out of an image is by using the Zoom tool. Go ahead and select the Zoom (Z) tool from the Toolbox. By clicking on the image with the Zoom tool, we can zoom in on the image at predefined increments. To zoom in on a certain area only, click and drag the Zoom tool to select which part of the image to enlarge. To zoom out, hold down the alt/option key and click on the image. You can see that the plus sign on the magnifying glass changes to a minus. Finally, double clicking on the Zoom tool in the Toolbox, will set the image to 100%.

There are also some very convenient keyboard shortcuts that enable us to change how the document is viewed. These are important shortcuts and you will save yourself a lot of time by learning them now. They can also be accessed through the View menu.  

• Zoom out  - Ctrl/Cmd  -
• Zoom in  - Ctrl/Cmd  +
• Fits the image on the screen -  Ctrl/Cmd  0
• Zooms image to 100% - Ctrl+alt 0 / Cmd + Opt 0

To demonstrate the hand tool, let’s zoom the image to 100% (Ctrl+Alt 0 / Cmd + Opt 0). Now click on the Hand (H) tool in the Toolbox and use it to drag the image across the screen. If any other tool is selected, hold down Spacebar to drag the image. If we now double click on the hand tool in the Toolbox, the image is fitted on the screen again, similar to pressing Ctrl/Cmd 0

Duplicate

Once you have an open document, it is easy to make a duplicate. Go to the menu bar and select Image>Duplicate and enter a name for the duplicate image.

Size & Resolution primer

Before we move on, we need to look at the concepts of image size and resolution. The principles that follow are the basis for working with any digital image file. Every time you use Photoshop you will have to take into account the following information.

Bitmap vs. Vector

All digital image files are considered either Bitmap or Vector images. Photoshop can work with both Bitmap and Vector images and can even have both in the same document. There is a fundamental difference between the two and each has specific applications.

Bitmap images are made up of dots or pixels of different colours, in a grid, that form an image. These pixels allow subtle colour and shade gradations. Bitmaps are the most common image type for continuous tone image such as photographs because of the detail that can be displayed. Bitmaps are resolution dependant though and cannot be enlarged without a loss of quality.

Example: When you open an image, there are a certain amount of dots or pixels that make up that image. When you enlarge that image, pixels have to be “enlarged” and this causes jagged edges in the image, known as pixilation.

 

Vector images are made up by mathematically defined lines and curves, called vectors. The information in the image file tells the software displaying the image (or printer printing it) where on a page lines, curves and colours should be displayed. Vector images are resolution independent. This means that they can be scaled without any loss of quality. Vector images are normally used for graphics that must retain crisp lines and edges at various sizes.

Example: When you open a vector image, the information in the image file tells Photoshop to draw a block, on an A4 document, which is 2cm from each of the four edges of the page. When that image is enlarged to an A3 document, the block is still going to be 2cm from each of the four edges, but now just on an A3 size document. The quality stays the same.

During this course we will be working mostly with Bitmap images (photographs).

Image size & Resolution

We have already established that bitmap images are made up by pixels. Now let’s look at how pixels, resolution and document size relates to one another.

Open S2_Ford.jpg from the CD. With the image open, click on the Image menu and select Image Size. This opens the image size dialog box. In the dialog box we see several sections: File size, Pixel dimension, document size and some resampling options.

• The Image size shows the file size of the opened document. This might differ from the size you see on you disk, because of file compression. More on this later though.
• The pixel dimension is the number of pixels along the height and width of an image.
• The document size is the physical size an image will be when printed.
• The resolution is the amount of pixels per inch.

To illustrate the relationship between them, here is a bit of math for you.

Pixel Dimension = Document Size x Resolution

We can see that our image has the following attributes:

• A file size of 6.16Mb
• A pixel dimension of 1800 x 1197 pixels
• A document (output) size of 12” x 7.98”
• A resolution of 150 pixels per inch (ppi)

The action of changing the amount of information in a file is called Resampling. In the image size dialog box we have the option of resampling an image or not.

If we deselect the Resample Image option, and halve the resolution to 75ppi, the document (output) size doubles to 24” x 15.96”, but the pixel dimensions and file size stay the same (no pixels were added or taken away).

If we leave the Resample Image checkbox checked, any changes we make will affect the pixel dimensions and file size of the image, adding or removing pixels from the file. Therefore if we double the resolution to 300ppi, the pixel dimension will also double to 2600 x 2394 pixels and the file size will increase (pixels were added).

When resampling an image (Resample Image checkbox checked), the Constrain Proportions option is available to us. By keeping this option checked, changes to the document (output) size, will not change the aspect ratio of the image.

Example: If the Constrain Proportion box is checked and we change our document width to 24”, the height will also change relative to the proportion of the image. In this case 15.96”. If the Constrain Proportion box is unchecked and we change the width to 24”, the height will stay the same at 7.98”, changing the aspect ratio of the image.

Canvas Size

The Canvas tool is used to add or remove workspace around an image. Canvas size should not be confused with Image size. To demonstrate the Canvas size tool, let’s work with image S2_Ford.jpg from the CD again.

With the image open, click on the Image menu and select Canvas Size. In the dialog that follows we find three sections:

• Current image size
• New image size
• Canvas extension colour

The current image size shows the current file size and the current document (output) size.

In the new image size section, we can specify a new document (output) size for our image. If the values are larger than the current image size values, the canvas will increase in size. If the values entered are lower, your image will be cropped.

By checking the Relative checkbox, we can change the canvas in increments. A negative value will decrease (crop) the image.

The anchor blocks specify where on the new canvas the original image is positioned.

The canvas colour extension enables us to specify what colour the new area will have.

Exercises 2.1

In this exercise we will add a 0.1” white border to the canvas size, followed by a 1” black border to create an elegant two tone border.

1. Open image S2_Ford.jpg from the CD.
2. From the Image menu select Canvas Size.
3. Check the Relative checkbox and add 0.1” to the width and height. Make sure that the Canvas Extension colour is set to white. Click OK.
4. From the Image menu select Canvas Size again. With the Relative checkbox checked, add 1” to the width and height making sure the Canvas Extension colour is set to black. Click OK.

We are left with an elegant two-tone border around the image.

Crop Tool

With the Crop tool we can crop our image to alter the composition. When the crop tool is selected we can find some additional settings in the Options bar. We can specify the width, height and resolution the image should be after cropping.

Exercise 2.2

1. Open the image S2E2_Butterfly.jpg from the CD.
2. Select the Crop tool from the Toolbox. Click and drag over the image, cropping out the excess green on the left.
3. To adjust the size of the crop, move the mouse to one of the corners of the cropping frame until it changes into an arrow and readjust it.
4. To finish the crop, double click inside the frame or press enter/return on the keyboard. To undo the crop click on the Edit menu and select undo (Ctrl+Z / Cmd+Z).

Image Modes

Before we go on, let’s have a look at Image Modes. Image Mode refers to the colour space (Grayscale, RGB & CMYK) and colour depth that a particular image has.

Images in Photoshop have one or more colour channels. Images get their colour from colour channels. For our purpose we are only going to look at the three main Image Modes: Grayscale, RGB & CMYK.

Grayscale images only have one colour channel, since the image is made up of only one colour, gray, and different shades thereof.

RGB images are made up from at least three different colour channels: red, green & blue. These three channels combine to form a full colour image. Since a monitor or television displays information in the RGB colour space, these images can be displayed accurately across a large selection of devices.

CMYK images are made up of at least four different channels: cyan, magenta, yellow & black. These colours represent the different colours of printing ink used. CMYK images are used for printing magazines, newspapers etc. using colour separations.

Images in Photoshop can also contain additional channels, called alpha-channels, which can store information about spot colours, masks and selections.

The second element of colour modes is the bit-depth of an image. Bit-depth refers to the amount of different possible colours an image can contain. Bit-depth is calculated per channel, therefore the more channels an image has, the greater the bit-depth will be. Most images are 8-bit images.

Example: An 8-bit grayscale image can display 256(2p8) different shades of gray (It has only one channel)

A 24-bit RGB image (8-bits x 3 channels) can display roughly 16 million colours (2ttp24).

 

Saving Images

Now that we have changed an image, we have to save it to be able to use it at a later stage. To make the image as accessible as possible, we will save it in a jpg format. This will make it easy to distribute (via email or the web) and easy for other people to access it. To save the image, do the following:

• Go to the File menu and click Save As
• Browse to the folder where you would like to save your image
• Give the image a unique name
• Click Save

The dialog box that follows is used to set the compression/quality of the image. A high number will produce a good quality file, but a larger file size. A lower number will produce a poorer quality file, but a smaller file size. A good compromise is to set it to 9. Click OK. Your file has now been saved.

Section 2 Quiz

1. What happens when you double click the Hand tool in the Toolbox?
2. Which type of file is resolution dependant?
3. What is the document size?
4. Which command do we use to add space to the outside of a work area?
5. How many colour channels do a RGB have?