Since you did not cross and did not cause any accident or traffic jam .. you will not be fined fully. It will be minimum amount of Qrs. 500/- But it depends on the video, coz after seeing the picture, they will also look into the video footage. If they find you did not cause any accident or jam.. they may not fine you. It happened to me last month. I crossed the signal and reach upto the middle but when realized that it was my mistake due to absense of mind, I just came back but by this time I was clicked by the camera 3-times. But so far I was not charged even a single penny coz they saw the video and found that it was not intentional.