I have the 12-40mm f/2.8 lens for my EM-1. I am considering the 9-18 for wide angle landscape shooting, but I am wondering how much wider 9mm really is compared to 12mm. Are there any 7or 8mm primes that are rectilinear that might work better? I really don't want to wait a year or more for the new 7-14 f/2.8 for a good wide angle. I would be OK with a manual focus for this purpose. Thanks for any suggestions.