Higher res pics on OPtio S4

So far as the camera itself is concerned, dpi is a meaningless statistic. All that matters is the number of pixels. Apart from file size implications, the more the better. dpi only comes into the situation when you display the image. If you display the image on the screen at '100%', or 'full-size', then (somebody told me) this is roughly, or traditionally, at about 72dpi. If you size a 6 megapixel image to A4, then it's at around 250 dpi (I forget the exact figure but you see what I mean). dpi just stands for dots per inch - it's a measure of how closely or not the pixels are packed together in the displayed image. In theory the closer together (higher dpi) the better. People have in their head that 300 dpi is necessary for a good, detailed print. Actually without very close scrutiny most people can't tell the difference above about 230. The bigger the print you do, obviously the lower the dpi becomes. It's complicated by the fact that most printers will 'resample' the image anyway in their own software, so that even if you are printing a picture at a very low dpi figure, the printer will create dots to make up the deficit, although the result will be a softer image. Which is why you don't normally see pixellation on your home printer, even though the dpi figure may be very low ...

This resolution doesn't matter to most software. It doesn't change the image at all, just occasionally the size it is displayed (only if the software scales the image according to the resolution, which most don't). This having been said, I doubt there is a way to change it in camera. But you could certainly change the XResolution and YResolution meta information with any good EXIF editor. Also, Photoshop can do this too, but it will mess up other things in the meta information. You should be able to script either to apply this change to a number of photos at once.