Snagit (Windows): Effect of Changing DPI on Capture Quality

Snagit contains a feature that allows you to change the DPI of the image that you captured. However, changing the DPI does not change the quality of the image; it only makes prints smaller. DPI, in relation to screen capture, is one of the most complicated aspects of screen capture.

Let's define the two important terms within an image.

Pixels

If you look closely at the monitor, you will be able to pick out small squares of color within each object on your screen. Each small square, which are referred to as pixels, make up the images on the screen.

Dots per Inch (DPI)

This can also be replaced with Pixels per Inch (PPI). When referring to Dots per Inch (DPI), a single pixel in an image is one dot. So, each dot printed on paper represents one pixel within the image. The DPI setting allows a user to define how many of these dots will fit into an inch on the page. DPI is also often referred to as a printing resolution.

Snagit will capture the exact pixels that are being displayed on the screen. When capturing the images, the DPI does not yet come into play. Once the image is captured, you then set a DPI for the capture so that it will print at that specific DPI. However, changing the DPI setting does not add or remove any pixels to the captured image. Changing the DPI will only change how many dots (pixels) will be printed within an inch on the page. Because of this, increasing the DPI for an image will make it print smaller. This is explained by this formula:

  • Image Size/DPI = Printed Size

Some examples of this are:

  1. A 100x100 pixel image is printed at 100 DPI, the image would then be 1 inch by 1 inch when printed.
  2. A 300x300 pixel image is printed at 100 DPI, the image would then be 3 inches by 3 inches when printed.
  3. A 300x300 pixel image is printed at 300 DPI, the image would then be 1 inch by 1 inch when printed.

However, if a 300x300 pixel image is printed at 300 DPI, but you wanted the size to be 3 inch by 3 inch, it would not be possible.  If you enter these numbers into the formula, they would not calculate to a print size of 3 inches:

  • 300 pixels/300 DPI = 1 inch

In order to print this image at 3 inches with 300 DPI, you would need to enlarge the image such that when dividing the image size by the DPI, you would get a printed size of 3 inches. This means that your image size would need to be increased to 900 pixels to divide by 300 DPI would generate a print size of 3 inches:

  • 900 pixels/300 DPI = 3 inches.

One thing to remember when you are using Snagit, you are capturing exactly what is on your screen. You cannot capture more than what is being displayed. However, you can scale what you captured to a larger size and print the image to a higher resolution to get your desired print size.