ND filter for capturing moving water

[anish]

Hello,

 

I'm looking to get an ND filter so I can slow down shutter speeds to

get flowing water to look nice and silky. This is the first such

filter I am going to buy, so I have no idea what strength I need. I

would like to start with just 1. I most frequently shoot Velvia 50

at wide to normal angles (24-50). 2 stop? 3 stop? 4 stop? Any

suggestions?

Thanks,

 

-Anish

[sheldonnalos]

If you are shooting Velvia 50 in any sort of shady conditions (where most running water tends to be), you'll have a hard time having the water be anything but smooth and silky.

 

Water starts to blur around 1/30 to 1/15 of a second, and then gets smoother and less defined from there. I find exposures of 2 seconds or more cause the water to lose too much definition, but your tastes may vary.

 

If you're already shooting and are not getting the effect you are looking for (and have the aperature stopped down for the longest possible shutter speed, f/16 or f/22), then I'd try a 2 stop ND filter. A polarizer might be a better suggestion, since it is more useful in a broad range of situations (darkening a blue sky, cutting down reflections, boosting saturation) and would serve a roughly a 2 stop ND filter as well.

 

Hope this helps!

 

Sheldon

[michael_zimmet]

I often use B+W's 6-stop (1.8) ND filter for waterfall pictures.

 

Photographed under somewhat overcast conditions - call it 2 or 3 stops darker than sunny conditions - yields a non-filtered exposure of around 1/30 - 1/60 @ f/8, assuming ISO 50 film is being used. (Since the f/16 rule would call for an exposure of around 1/60 @ f/16, given sunny conditions.)

 

6 stops more exposure turns 1/30 - 1/60 @ f/8 to 1 - 2 sec. @ f/8. Which I find near ideal for most types of flowing water.

 

But that's just me. The fact that I like the look at 1 - 2 sec. exposure doesn't mean you'll like it. Only you can determine what sort of look you like. Moreover, subjects differ - a trickle of water in a stream during a dry season, may not merit the same exposure time as a roaring waterfall during the spring melt. Nor can one always shoot on an overcast day - sometimes we have to shoot on brightly sunlit days, despite any inherent problems with such lighting.

 

Some flowing water images I took with 6-stops of light attenuation (a 3-stop B+W ND filter, plus my Canon G3's internal 3-stop ND filter) may be found at http://www.time4email.com/falls/

[davidroossien]

On a typical shady day at a waterfall, shooting at f11 to f16, my exposures are 1-2 seconds, so how long do you want your exposures to be?

[dogbert]

I do quite a bit of this and find a 4 stop ND most useful. You will probably want to get a polarizer at some stage and this can serve as a 2 stop. Combine a polarizer with a 4 stop ND and you will get 6 stops, which I think would be pretty much all you need in most circumstances.

 

Overcast conditions are generally less contrasty and therefore good light for this type of shot. In such light, a 4 stop ND, f22 and ISO 50 or 100 should get you a 0.5-2 second exposure, which is where most would suggest you want to be.

 

Make sure you bracket by varying shutter speeds, as the difference between say 0.5 and 2 seconds is normally quite noticeable, and it is hard to pick in advance which shutter speed will produce the best effect.