I've not used HP4 for anything, but am a big fan of Delta 100. Selfishly, I think it'd be great to have that as an option. Actually, I was initially pretty surprised that this 8" roll film they offered was so fast. It works beautifully, but I wasn't expecting something as fast as HP5. As an aside, historically speaking, does anyone know what film speed was originally used with these cameras when new? I'm sure it wasn't 400.