Saving and Resizing
If you're just beginning to use software to edit and adjust your photos, first things you need to learn are to save and resize your photos. These functions can be used for different purposes in various situations, i.e. for emailing your pictures to friends and relatives, printing your images or publishing them on the Web.
First of all, let's go through the "Save As" option in the File menu. Use it whenever you come across an image that you like. "Why ‘Save As' instead of just ‘Save'?", you ask. First of all, the "Save As" option gives you control over where the file is going to be located and in what file format it is going to be stored. "Save As" is also very useful when you are doing a lot of work on a photo and make a lot of changes to it. Make sure you save your picture to a separate file on every new stage of processing, so if you screw up at some point, you can always return to an earlier version.
If you need to resize your photo, you should also save it first, then resize, and then use the "Save As" option again to save the resized picture in a file with a name that indicates its new size (larger or smaller).
Now, when we know about saving, let's learn about resizing. Basically, resizing is changing the picture's size without changing the pixels. This may sound somewhat confusing, but it is absolutely not. Actually, what you do is change your picture's resolution making it cover more area, without changing the file itself. For example, you change resolution from 300 pixels per inch to 72 pixels per inch; your picture seems larger, but the file actually remains the same, you just shuffle things around in it.
These features will help you a lot since you are probably going to print, email or publish your pictures on the Web quite often. And every one of these actions requires resizing in most cases. For example, you may want to make your image smaller to make it email-friendly or resize it to fit a specific printing format. You can easily resize your images in Photoshop by using the Image Size command. Change anything you need about the picture's size and resolution in its dialog box.
One more thing: If you want to change your picture in a way mentioned above (change resolution without changing the overall size of the file), you should keep the "Resample" checkbox unchecked. If you do, you can make any changes to your image without being afraid to do any damage to it. On the other hand, if you do want to change the file size (for example, to be emailed to a friend), you need to check the "Resample" checkbox. By doing this you will be able to reduce the overall pixel dimension - that will decrease the size of the file. Again, be sure to use "Save As" option to save the smaller version, as well as the original image.