If you insist on bringing a camera into this madness of the CHUPINAXCO, we suggest that you wrap your camera completely in a waterproof bag. Or, we suggest that you bring a waterproof camera, due to the huge amounts of champagne, wine, mustard, mayonnaise, eggs, or other colorful condiments and refreshments that participants throw upon each other! We suggest that you do NOT bring your favorite, expensive digital camera into these crowds - your camera will either be ruined with the above mentioned champagne, wines, etc...or, the professional pickpockets may very well add your camera to their collections of San Fermín contraband! See pictures here, which show the density of the crowds that gather for the chupinaxco.
Watch this video for more information: http://www.sanfermin.com/index.php/en/la-fiesta/txupinazo
More info on what to expect at the CHUPINAXCO will follow in another post.