Is my photo file large enough for the selected format?
For an optimal photo print we work on the basis of 300 ppi.However, in The Netherlands we use centimetres, not inches. 1 inch = 2.54 cm. This is why we adopt (300/2.54) = 118 pixels/centimetre as our baseline in attaining an optimal print.
So, 300 pixels/inch is the same as 118 pixels/centimetre.
To now calculate whether your photo file is good enough for the selected print format, you divide the number of pixels (length or width, it doesn’t matter) by the number of centimetres of the print.
- The image is 3000 x 4500 pixels
- The print should be: 20×30 cm
- The resolution of a photo this size is: 3000/20 cm = 150 pixels/centimetres (As the length and width of the file are in proportion to the print sizes, you only ever have to calculate using the one side).
We just saw that 118 pixels/centimetre make for optimal photo quality. So, this photo has more than enough pixels for an ultra-defined print in this format. It’s only by looking at the number of pixels a image has that we can determine whether a photo file will be large enough for a specific print size.