After you publish a filter you can see a detailed statistics on how many impressions of the filter you have, how many people took a picture with the filter and how many people actually shared the picture with the filter. Those are the main metrics that can tell you if the campaign was successful or not. The number of people who saw the filter is the number of people who saw your brand! The more people share the picture, the more people come in contact with your campaign. Very simple, yet very powerful.