I sympathise - the relationship between size and resolution is not entirely straightforward and is complicated by the resolution of the medium you are using for display !
For example, my monitor has 1920 x 1080 pixcel display so any image that size or bigger displayed at 'full screen' will appear that size. I use quite a few of my photographs as wallpapers, almost all of them taken with a DSLR which produces images in classic 35mm format - 4 x 3 - and approximately 4000 x 3000 pixcels. I usually process these before using as a wallpaper just to reduce the file size since my screen cannot reproduce a 4k x 3k image fully. I normally reduce the width to 1920 pixcels using PhotoZoom and then crop the image to 1920 x 1080 in a package similar to PhotoShop so as to finish up with an image that fits on my screen without any distortion.
However, if I was to print that identical 1920 x 1080 image in a glossy magazine - think Vogue or Scientific American - which print at approximately 600 dpi (dots per inch) the image would come out at about three and a bit by nearly two inches. If, on the other hand, I sold it to our local newspaper - who print at approximately 100 dpi - that image would come out at nineteen by eleven inches !
What I was taught years ago, working with B&W 35 mm film was you never throw resolution away. You always keep the original image in the condition in which it started. In digital terms if you want a larger or smaller image, make a copy and play with the copy. Apart from anything else, if you totally mess up the copy you can always go back to the original and make another copy. If you mess up the original - you are *** ( supply appropriate verb of choice !).
PS - I've been using the flag for quite a while, certainly from before Alex. Salmond got on the referendum trail.
Edited by Chris Cosgrove, 09 March 2015 - 08:25 PM.