Instagram will soon begin sharing your personal data with Facebook, according to an update on the photo-sharing service’s privacy policy. While you won’t have a choice whether Facebook has access to the information about you gathered by Instagram (or vice versa), the company assures users that your photo-sharing settings will remain in your control.

“We’re updating our Privacy Policy to highlight this new collaboration, but we want to make sure you understand that you still have control over who sees your photos,” writes Instagram. “You still get to choose who can see your Instagram photos, and you still get to choose whether you post your photos on Facebook.”

In a blog post about the policy change, Instagram reiterates this point, saying, “Nothing has changed about your photos’ ownership or who can see them.” The company says greater sharing of data between Facebook and Instagram “means we can do things like fight spam more effectively, detect system and reliability problems more quickly, and build better features for everyone by understanding how Instagram is used.”

Instagram has already updated the “Parties with whom we may share your information” portion of its privacy policy to read:

We may share User Content and your information (including but not limited to, information from cookies, log files, device identifiers, location data, and usage data) with businesses that are legally part of the same group of companies that Instagram is part of, or that become part of that group (‘Affiliates’). Affiliates may use this information to help provide, understand, and improve the Service (including by providing analytics) and Affiliates’ own services (including by providing you with better and more relevant experiences). But these Affiliates will honor the choices you make about who can see your photos.

“Affiliates,” of course, refers to Facebook. Also note the “better and more relevant experiences” line. This type of vague, subjective language in a legal document (i.e. the privacy policy) may give cautious users pause, as it is impossible to decipher whether “better” means better for you, or better for Instagram and Facebook, or both. Point is, we just don’t know what that means. We have reached out to Instagram for clarification, and will update this space with any response we receive.

These changes to Instagram’s privacy policy should come as no surprise; Facebook effectively announced that it planned to share and collect more data from Instagram when it put its own policy changes up for a vote in November. Facebook users who voted on the changes overwhelmingly opposed them. Because less than 1 percent of Facebook users voted on the policy changes, however, Facebook still plans to put them into effect.

Thought some changes are already in place, the full versions of Instagram’s new privacy policy and terms of service will go into effect January 16, 2013.