Preparation Guidelines & Definitions
Print Resolution

Image files submitted for print must have an effective print resolution of at least 300 pixels per inch (ppi). IDoPrint.com's preferred print resolution is 350ppi. We print at a line screen of 175 lines per inch (lpi). Printing at a higher line screen produces cleaner, sharper images. Most online print vendors print at lower screen values of 133lpi to 150lpi. The ideal image resolution for printing CMYK, sheet fed offset is calculated by multiplying the halftone screen value by two. Using that formula the ideal image resolution for 175lpi is 350ppi. Images saved at 300ppi, although not ideal, will print just fine.

 

Please be sure that your images are not scaled in such a way as to push their effective resolution below 300ppi. There is a fixed relationship between and images pixel dimension and it’s effective print resolution. To illustrate the relationship between pixel dimension and resolution, consider an image with a pixel dimension of 600 pixels x 600 pixels. If we set its size to 2” x 2”, the image’s print resolution is 300ppi.The relationship is fixed. Any change to the image’s size changes its print resolution. Increasing the 2” x 2” image to 4” x 4” decreases its print resolution to 150ppi. Conversely, decreasing the image’s size by 50% increases its print resolution to 600ppi. Be careful not to scale cmyk or grayscale images to a size that would make their print resolution less than 300ppi.

 

Digital cameras differentiate resolution settings by pixel dimension. A digital camera may offer photo resolutions like 1600 x 1200 or 600 x 800. To determine the maximum size a digital photo may be printed simply divide each number by the required print resolution.To achieve the required 300ppi, a digital photo taken at 1600 by 1200 can be printed at 5.3” x 4” or smaller. (1600pixels/300ppi x1200pixels/300ppi).


For an illustrated and detailed discussion of image resolution along with a resolution calculator, please go to:

Go Back