I have a useful mnemonic for you: “For a flow, go slow”.

Meaning if you are picturing something that happens as a continuous flow, you should use a slow shutter speed, to capture it as that flow.  Like this, a few years ago:

To do this I did the following:

1. Defy death by climbing down an unofficial trail.
2. Use a tripod.
3. Use a wide angle zoom lens (16-35mm, on a full frame camera).
4. Put a variable neutral density (ND) filter on the lens, set to its maximum darkness.
5. Camera on manual. Use 100 ISO and a high f/number; in this case, f/20
6. Now see what shutter speed I need (20 seconds).

And that’s it!

Notes:

• You do not always need a slow shutter. For the waterfall, 1 second would have been fine too. But the river looks better at that slow speed.
• At small apertures you will see sensor dust if there is a blank surface, like a sky, in the shot.
• Use the 2s self timer, or you will shake the camera by pressing the shutter button.
• Do not damage your equipment; it’s easy enough!

And you will get great pictures.

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This is a repeat post – because it’s still true.