I want to send some old photos of varying sizes and shapes to be printed in 8"x 6" format but I'm struggling to make it work. I've scanned them at 600 dpi, cleaned them up using Photofiltre software, then pasted each one on a grey background of 8" x 6" in portrait or landscape, depending on the original photo's shape. However, to make them fit the background and thus be printable in the centre of the background without cropping, I have to reduce the size of most photos. When I send the resulting images to an online photo printer, many of them are rejected as the resolution has been reduced too much. The minimum required for an 8" x 6" print is 2400 x 1800 px. I need to maximise the resolution and not crop the photos. How do I make this work?