This question has come up many times before and the consensus remains the same. For new items like cameras or lenses, it is probably not such a good idea. They will most likely cost as much or more than in the US and you risk the possibility of losing warranty support when you get back home. Folks have been told they must send the camera/lens back to the country of sale for such support, so any service would have to be done in Japan.

That being said, there are large Bic and Yodobashi Camera stores in both cities. The ones in Kyoto are very near the station - Bic is actually connected via the west entrance and Yodobashi is just north on Karasuma-dori about a half block.

Be prepared to be overwhelmed. Both of the above stores make the B&H superstore in NYC look small. Also, language might be an issue. Kyoto is more used to foreign visitors than other places, but when I visited Yodobashi Camera in both Sendai and Sapporo, I had to use my not-great Japanese, which was better than the clerk's English, to communicate.


EDIT: I see glenaa11 and I were typing at the same time. I agree with him that you are unlikely to match the Adorama or B&H rebate prices with anything you find in Japan.