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Understanding DPI and Pixel Requirements for Photos

DPI stands for "Dots Per Inch," a measure indicating the density of dots in a printed or digital image. The DPI value is crucial for determining the sharpness and quality of the printed image.

How DPI Affects Image Quality

  • Higher DPI: Indicates more dots of ink per inch, resulting in a sharper, more detailed image. Essential for high-quality prints.
  • Lower DPI: Means fewer dots per inch, potentially leading to a less sharp image. This may be sufficient for text documents or non-detailed images.

Pixel Requirements for Photos

The required number of pixels for a photo depends on its intended use (digital or print) and the desired display or print size.

For Digital Displays

Modern screens typically display images at 72 to 96 DPI. For a full-screen image on a 1920x1080 (Full HD) display, the image should be 1920 pixels by 1080 pixels.

For Printing

High-quality prints usually recommend a DPI of 300. To calculate the required pixels for a print, use the formula:

                        Number of Pixels = Inches x DPI
                    

Example for a 5x7 inch photo print at 300 DPI:

                        Width: 5 inches x 300 DPI = 1500 pixels
                        Height: 7 inches x 300 DPI = 2100 pixels
                    

So, a 5x7 inch photo print at 300 DPI would need an image with a resolution of 1500x2100 pixels.

Note: While a higher DPI results in better print quality, there is a practical limit. Beyond a certain DPI, the improvement in quality won't be noticeable to the human eye at typical viewing distances.