how to call different image sizes

Hi All-

I'm trying to make the photo page dynamically select the appropriate image size for the viewers screen resolution. I have found a jQuery tutorial that I think would work but I need to know how to call the different image sizes.

When I'm in debug mode I can see where all the image sizes are under $theme.childern.itemlinks, but it seems that is used to populate the pull down menu to link to those images. I don't see what I could use to call the resized images.

Any help would be much appreciated.