Making Good Prints - File Size

Setting aside artistic considerations such as composition and lighting, focus etc. the most common issue is the number of 'pixels' in your file, which makes up the file's size. The challenge here is the most common file format is JPG which is compressed. With compression, a complex scene such as a winter thicket with lots of branches results in a larger file size than an image which is composed of smooth areas like sky or calm water, even though the images may have the same number of pixels. This makes it difficult to determine how big a JPG file can be printed successfully based on file size alone.

To determine whether or not a file has sufficient pixel information to create a good print we have to do a little math. To make a good print you need at least 200 pixels for each inch of the print size, so a 4"x6" print requires at least 4 x 200 pixels by 6 x 200 pixels, which is 800 x 1200 pixels. As an uncompressed file, such as a TIF, this file is 2.7 megabytes. As a jpg however, this same file could be anything from 360 to 460 or more kilobytes.

To make things a little easier, the following chart illustrates how print size relates to MegaPixels ( the way digital cameras are rated ), uncompressed or TIF file size, and the possible file sizes for simple and complex ( think smooth sky versus tree branches ) compressed JPG files.

Using this chart, you can see that if your file is less than roughly 360 kilobytes (KB) in size it will not make a good print, even at a small size such as 4 x 6 inches.