A Bloomberg Businessweek article
discusses the effect of the flooding on Nikon's ability to deliver DSLR cameras.
"Nikon’s inventory of SLR cameras will probably last for about a month and the effect on earnings would be negligible should the company resume the plant’s operation within a month, Hisashi Moriyama, a JPMorgan analyst in Tokyo, said in a report dated yesterday."
"Suspensions lasting two months could cut Nikon’s revenue by 30 billion yen and operating profit by 5 billion yen to 10 billion yen, he said."
Not mentioned was the disruption to Canon production. At this point, I'm only aware that Canon's inkjet production has been affected.