Django read only/view permission on models + row level permission -

i making photo sharing application using django framework. stuck 2 problems

1) user has uploaded photo can edit photo. other users cannot edit photo. can see/view list of photos users. , can add photo under username

2) need define row level permissions 1 of functionality. eg - rating of photo other users. now, u can when u give write permissions user. if give write permissions, user able edit other stuff (name, album etc..) not want. want user can edit ratings.

i tried searching answer not able any.

would glad if can help

1) in picture class, have variable hold username of person uploaded picture. in editing view, make sure aren't confining editing ability username.

2) @ django tutorial @ https://docs.djangoproject.com/en/1.5/intro/tutorial01/ , head on part explain how create voting in poll app. should give foundation project.