Home › Forums › CSS › How big (file wise) should my background image be? › Re: How big (file wise) should my background image be?
First, monitors do not have dots they have pixels, so it should really be PPI. The term DPI is old and is being misused all the time. DPI is only related to printer. Number 72 refers to the number of pixels that can be placed per inch on the average monitor, there’s no reason to increase it because the monitor can not resolve it. Now what you must be confused about is resampling. This should always be off when changing DPI because, if left on, you are artificially adding pixels. Bad idea.
So whenever you’re printing, you want to leave the pixel dimensions alone and change the document (print) size or (DPI) to fit whatever size you need. So you can get away with printing poster size image with 150dpi resolution, because the viewing distance for that print will be greater.
Think of it as input/output or PPI/DPI (digital capture device like dslr / printer). Pixel dimensions should not change throughout the chain.