Photographing Waterfalls
March 10, 2013
Photographic Technique for Waterfalls, Streams and Cascades
There are few simple issues that one should consider when photographing waterfalls:
- weather
- filter
- exposure
The best light conditions to make photographs of waterfalls are during cloudy skies. Sunlight will further exaggerate the usually high contrast between flowing bright 
water and dark surrounding rocks. Resulting high dynamic range of the scene will be difficult to capture with the current sensors. In addition, less light during cloudy weather allows using longer exposure time. Additional consideration is the timing since the previous rainfall. Logically the water flow through the waterfall will increase after heavy rain and decrease in the dry season. But immediately afterwards heavy rain can also result in muddier, less clear water, so a day or two after rain seems to be generally the optimal timing.
Photographing waterfalls is one of the few remaining occasions when I would still use a polarizing filter. In many other scenes one can easily reproduce the filter effects in 
post processing, but in the case of wet rocks, the polarizing filter allows decreasing the amount of the reflection of the polarized light from the wet surface of the rocks and ability to 'see through' it. One needs to experiment with the 'amount of polarization' to achieve the right balance between preserving the desired reflections and removing the unwanted ones.
The polarizing filter has another advantage - it decreases the 
amount of the light hitting the sensor by about 2 stops. Generally landscape photographers struggle with not enough light. Waterfalls are frequently the opposite, and some would use neutral density filters to further decrease the amount of light hitting the sensor. The reason for this is to achieve 'veil-like' appearance of waterfalls.The get this effect one must use sufficiently long exposure time. How long? It depends on the height of the waterfall (physics of a free fall :-), the personal preference for the amount of 'blurring' effect or the speed of the current in the cascades 
(the longer the exposure time, the more 'blurring').Generally I end up using exposure times 1/2 - 5 s and I accept apertures up to f13 - f16.That of course requires tripod. One takes several properly exposed shots with different exposure times to avoid guessing the correct one. Later during post processing one can then choose the the best one. To make this shooting process efficient (frequently there is a lot of mist in the air around tall waterfalls, condensating quickly on the front filter and camera) -I use manual mode: 
after determining the correct exposure I shoot several shots with increased/ decreased exposure time and adjusting aperture accordingly. (One click on the 'exposure time wheel' will generally require one click on the 'aperture control wheel' in the opposite direction to maintain overall exposure.)
And be careful on the wet, slippery rocks around waterfalls...