There are several reasons why you will want to crop a photo: the subject is too small, there are distracting elements, or the composition can be improved.

When the subject of your photograph is too small, you can increase its size by cropping off the edges of the photo. This creates an artificial zoom effect that lets you frame the subject exactly the way you want.

Sometimes distracting elements will find their way into your photographs. A serene photo of a lake might be marred by the presence of a garbage can. A tree limb might be intruding on a photo of your best friend. In these cases you can eliminate the distracting object by cropping it out of the photo.

Finally, you just might want to adjust the composition of your photo. Let’s say that you only have a couple of seconds to take a quick snapshot of a scene. You don’t have a lot of time to think about where eveything is positioned in the photo.

You preview the photo in an image browsing program and realize that the composition could use some improvement. Maybe you’d like to apply the Rule of Thirds to it, or maybe a different view of the scene will create more impact. You can once again use cropping to do the job.

In every one of these cases you can dramatically improve an otherwise ho-hum photo with just a small amount of cropping. Sometime no amount of cropping is going to fix a photo, and this is one you have to discard. But many times photos can be improved with some cropping and you will discover that potential discards have now become keepers.