Do they have their logo trademarked or copyrighted? If so, you may have to change your logo. Of course that works both ways. If you have your logo registered, you could have them change theirs.

What is their photography like compared to yours? Are you targeting the same type of market such as weddings? If you have different styles and markets, I wouldn't worry to much about it. If you're shooting weddings, and they are shooting nature, chances are your customers aren't going to get the 2 of you confused.

If it were me, I wouldn't worry about it unless you are afraid of your customers getting confused and finding them instead of you. Is there web address similar to yours? For example, do they have katzphotography.com to your katzphotography.net? If that were the case, I think I would try to come up with a different name to try to separate myself from them.

Just my thoughts.