[ctaulbee]

First thing is that pixels are not a measurment it's just another name for the dots on the screen or dots of ink from a printer. As all images are made up of pixels or dots.

With DPI being dots per inch or number of ink dots printed per inch. This also means that the DPI sets the resolution or quality of the image. So the higher the DPI the higher the resoulution or quality the printout will be. The standard used for most general printing is 300dpi.

A standard case cover image that is 3240 X 2175 pixels @ 300dpi will equal 10.8in X 7.25in printed. If you change the DPI or "dots per inch" to say 150 and keep the cover image physical sixe at 10.8in X 7.25in then the pixel count will drop to 1620 X 1088 so the resolution or quality will go down as there will be 50% less ink dots per inch when printed. But it will still be the same physical size.

Remember when you see pixel sizes here it is assumed that your talking about a 300dpi image. so dividing the pixels by 300 will give you the inch size of the image printed.

But remember that an image that is 3240 X 2175 pixels can print at different sizes depending on what the DPI is set to. Because as the DPI goes down and the pixel count remains unchanged the image will grow larger physically as it is a ratio and the dots in effect are being spacing out from each other. As the DPI goes up the dots will get closer together so the image will shrink if the pixel count remains unchanged.

So... for a 3240 X 2175 pixel image with the following two DPI settings:

First if the DPI is set to 150dpi then printed it would printout at 21.6in X 14.5in on the printer.

Then the same image...

But with the DPI changed to 300dpi will now printout as 10.8 X 7.25in on the printer.

Yet both would be the same 3240 X 2175 pixel source image with only the DPI changed.

So you need to watch the Document Size vs Resolution under the Image Size Tab in PhotoShop.

Hope this helps.