Rivers, lakes and waterfalls make interesting photographic subjects but they are not without challenges. When photographing these subjects, watch for bright sunlight reflecting off the water. While it can often add to the image, it can also cause exposure difficulties and you may have to choose between losing shadow detail or having the reflections wash out.
The light meter in most cameras assumes that the ‘average’ of an image is what photographers call ‘neutral grey’. In most cases, this works reasonably well. However, snow and sand are both brighter than neutral grey and, if they comprise a significant portion of the image, the result will be an underexposed image. This is why snow and sand take on a dull grey colour in many photos. While you may be able to adjust this later, in your photo-editing software, the common solution is to increase the exposure by approximately one stop. If you can’t do this manually, check your camera’s instruction manual. Some cameras have a ‘beach’ mode designed to address this issue.
You’ve probably noticed that direct sunlight is not very flattering. It creates harsh shadows and most people can’t keep their eyes open when looking into the sun. The time-honoured ‘advice’, to place the photographer’s back to the sun, often produces mediocre results. In practice, if you can’t find a place in the shade, I suggest you try the opposite: Place the subject’s back to the sun, force your camera’s flash on, or use the other techniques outlined in ‘backlighting’. You may also want to experiment with commercially available or improvised reflectors, such as a large sheet of white cardboard.