Photography resolution is a measurement of image quality, so you may define resolution by how much detail is in your print. If your print has sharp detail you may consider your image to be of good resolution. If detail is blur in your image you may consider your image to have poor resolution. Good resolution is a direct result of having a large number of pixels in an image.
Digital images are made up of millions of small dots – each dot is called a pixel. Each dot contains a small piece of image information, and when added together with the other pixels you’ll get your final image.
Print resolution is measured in pixel per inch (ppi) or in dots per inch (dpi) – both hold the same value. 300ppi means that there are 300 pixels per inch or 90,000 pixels per a square inch.
