The reason the images on a CD from the lab are so huge (in measurement) is so you can use the images in either format. 72dpi is exactly 25% of 300dpi. If you want your 300dpi images to look as razor sharp as your 72dpi images do on line, the print has to be 75% smaller. In other words, an image that measures 44 inch x 56 inch at 72dpi would be the same quality as an image that measures 11 inch x 14 inch at 300dpi.
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