Assign tag to category

Here is the situation

I have photo blog. Where i post atleast 50 Photo per day. I have only few category to play with. I am looking for something that will do bellow work by itself while i upload a photo.

1. I have tags for certain photo category. Which i want to assign with these category.
2. So that when i change a category of an image it will automatically update its tags.

Please help. I am looking everywhere but could not find any. May be i am missing “correct keyword” to fine something that will do my job.