Tag use needs to be intuitive or it is useless. New people come in all the time, and one day that floodgate could open. It takes weeks to months to START to catch on to all the rules and expectations about tag use already, so a more complicated answer is not a solution...
I suggest leaving "photography" as a wide open tag, then ANYONE with a photograph can use it without irritating whales or bots. Create a "prophoto" tag, or something like that, so the onus of correct tag use us upon those who are entering contests or challenges. If they have figured out how to enter, they should have mastered appropriate tag use for their entries also.
As a newbie who got jumped on for "tag spam" (on a post that garnered less than a quarter) I am ADAMANT in my stance that intuitive tag use be allowed. Having people jump in, start to have some fun, then accuse them of spam over some obscure definition of a tag that they were unaware of is a real buzzkill, and nearly had me leave the platform completely.