Reconstruct raw data

Hey! Someone from ISI (Ida?) recently spent a bunch of time working on my computer and was reconstructing data from a .3mm scan into .4mm AND .25mm. My question is, if I do a 20 sec scan @.4mm and I reconstruct at .25mm, do I get any more information than I had at .4mm? It seems to me that one can reconstruct down (.3 to .4) but not up (.4 to .3). Any comments?