The score is based on the number of stars and reposts of each photo.
Note The scores are updated once a day.
The user's score is computed as the average of their photos' scores, weighed by time. The score of each photo is based on the number of stars and reposts. The time weight has been added to encourage users to upload more photos; without this, a photographer with a single photo with a lot of stars and reposts would dominate the leaderboard forever. This formulas are likely to be tweaked over time, check here for the latest details.
The formula used to computed the score is as follows (n is the number of photos posted by the user):
The time weight is computed like this:
If you have a photo with a score of 100, this is the impact of the weight