If you show up, and if the judge asks you who was the driver, and if you said it was you, well, you admit you were the driver, (PHOTO cannot prove who is the driver, hence NO demerit points!), and if you are not the driver, then that person should pay the fine.
There is an article I read from last Saturday MINGPAO Saturday magazine, it talks about fighting traffic tickets, it also talks about does it worth to fight photo tickets. Have a look