Field permission for Administrator
Install Disable Field module and install. After installation go-to admin/structure/types/manage/YOUR_CONTENT_TYPE/fields and edit the desired field. In the bottom, you can see DISABLE FIELD SETTINGS open that and you can choose to disable option in DISABLE THIS FIELD ON ADD CONTENT FORM? and DISABLE THIS FIELD ON EDIT CONTENT FORM?. In that Select Disable for certain roles and choose administrator. After that save and that field will be disabled in ADD/EDIT based on your selection