Saturday, June 24, 2006
Print quality
How large can one print a 3 megapixel digital picture before it loses true photo quality and gets all blurry and messed up? 3 megapixels is 3 million pixels is 2048 × 1536 pixels (which equals 3,145,728 pixels) and if 'true photo quality' were defined as printing at 300 ppi, then said image should not be printed beyond the standard 5 × 7 inch photo format. Just divide the pixels by the ppi count to get the maximum printable size, e.g. 2048 / 300 = 6.83 inches and 1536 / 300 = 5.12 inches.

Working backwards: Say you want to blow up that picture of Granny to A2 size (420 × 594 mm or 16.54 × 23.39 inches) while keeping true photo quality so that all her liver spots stand out, you would need a whopping (16.54 × 23.39) × 300 pixels, or 4962 × 7017 pixels, which equals 34,818,354 or 34 megapixels. Or you can wuss out and print it at 200 ppi, in which case you would only need the same image at 15 megapixels.

Someone should really metricise all this. In the meanwhile, go here for a megapixel calculator and here for a handy pixels-to-print chart.


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posted by Hong at 5:35 am | Permalink |


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