The default setup in Adobe Photoshop CS5 includes the creation of new images with a white background. There are many situations where a white background is ideal for your image creation, so you probably have not given much thought to adjusting that setting. But if you are planning to make a multi-layer image, or if you want to create a transparent PNG image for your website, then you have likely discovered that a white background actually has a pixel color value, and that value needs to be removed. There are a couple of different options when you want to learn how to make a transparent background in Photoshop CS5, so you can read this tutorial to determine which solution is right for your situations.
Create a New Image with a Transparent Background in Photoshop CS5
This is the simplest of the two solutions, and is certainly where you should be starting, if possible. Launch Adobe Photoshop CS5, click File at the top of the window, then click New. This will open the New window.
Click the drop-down menu to the right of Background Contents, then click the Transparent option.
Make any other necessary changes to the size and format of your new image, then click the OK button to generate your blank image. All of the empty space on your image will be transparent, provided that it is saved in a file format that supports transparency. If you are creating an image that will be posted on a website, you should probably use the PNG file format, as JPEG does not support transparency. Anything you add to the image will have the transparency that you define. You can choose the opacity for each layer by adjusting the Opacity option at the top of the Layers panel.
Change an Existing Background to a Transparent Background in Photoshop CS5
The solution to this problem is a little more complicated than the solution to creating a transparent background from scratch.
If you are working with a multi-layer image and the existing background layer is only the default white background, then you can delete that layer. Right-click on the Background layer in the Layers panel at the right side of the window, click the Delete layer option, then confirm that you want to delete the layer. Any transparency in your image should now be in effect.
If you have content on the Background layer that you want to save, then you will need to get a little creative to remove the unwanted background color.
You can use the Magic eraser tool (right-click the Eraser tool in the toolbox, then click the Magic Eraser Tool) to delete all contiguous regions of that color on your layer. If you are finding that this method is deleting some of the content that you want to keep, you can undo the erase, then modify the Tolerance setting at the top of the window. The lower the tolerance number, the more precise the magic erase action will be.
You can also unlock the background layer, then use the regular eraser tool to manually erase unwanted elements of the background.
One final option is to use one of the lasso tools to select the content you want to keep, press Shift + Ctrl + I to invert the selection, then press Ctrl + X to delete the unwanted background.
There is no one solution that is going to work in every possible scenario, but if you become comfortable with each of these tools you should be able to make a transparent background in Photoshop CS5 for just about any image that you encounter.