Checking the Focus: To check the focus on your photo, open an image on your PC using the Windows "Paint" accessory tool. You may enlarge the image by going to "View" then "Zoom" then "Custom".

Check the Size
Don't have a digital file? |
 |
Resolution of your image is only one of several things to check. You should also check the focus. |
Even though these two shots (above) look identical at a smaller size, when enlarged the one on the right is clearly out of focus. |
 |
|