I will be going to Kota Tinggi in Malaysia next week and am told that we will be able to see Fireflies at night during a boat trip. Any advise on the best way to capture the fireflies on photo? What would be a better lens to bring along - the Canon 24-70, 2.8 or the Sigma 18-35mm, 1.8? Any advise on setting the right exposure, ISO, shutter speed, etc. would be highly appreciated.