I don't know if there are any books on this subject or not. If there are, I have never run across either a book or an article on this subject. Most of what I know is from my only experience with a digital camera, a Kodak DC4800 which has a 3.1 megapixel resolution at its highest setting.
Right out of the camera, the images it makes are 30" x 20" at 72 pixels per inch (ppi). Since there are 5,184 pixels in a square inch and 600 square inches in the image we have a total of 3,110,400 pixels (3.1 megapixels).
I reduce the size down to 10" x 6.667" for archiving, which increases the resolution to 216 ppi. Different cameras have different proportions at different resolutions. There is no way of knowing what proportions a camera might have without getting the specs for it.
If the proportions for a 4.1 megapixel camera are the same as the 3.1 megapixel DC4800, then it would have an image of 39" x 26". If I reduced that down to 10" x 6.667" the resolution would be increased to 280.1 ppi.
That is very close to the 300 ppi resolution required for high quality commercial presses in the printing industry!
Personally, I have found that 150 ppi is enough resolution for the work that I do. At that resolution the stair stepping, obvious in low resolution images, disappears.
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