So... I was browsing the canon product line late at night.. and i came across the extension tubes. It seems to me that it will accept an EF-S or EF lens, but will only fit an EF camera (not that it matters, since all EF cameras take EF-S). So by doing this... have you converted an EF-S lens to EF mount? Also... since you would lose the focus at infinity b/c now the lens is too far away from the body... but is that still the case with the EF-S lens, since it would come into the extension tube more than the EF lens?