Maybe I'm not understanding ND filters?

I picked up a Hoya ND x4 filter, in hopes of getting those tired and played out flowing water images, since I love them. The filter was $10 on fleabay, so I figured it was a good one to start with.

I was able to get a 30sec shutter speed at f22, but I really didn't get the effect I was hoping to see. Is it that the water was pretty calm (I live on a canal off the Intercoastal in FL), or is the ND4 not dark enough for what I'm hoping to accomplish? There are some nice colored fountains (retirees like fountains I guess) I want to shoot during the day, but now I'm wondering if I have enough filter power.

This was 30sec at f22, 90mm, ISO 100. There is smoothing, but I was hoping for more. And yes, I know it isn't straight, but I was more interested in learning the filter, and didn't care about anything else.

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Well, your ND4(.6) is only going to get you two more stops, and if you took that in broad daylight, your shot seems about right. An ND8(.9) will get you 3. You can also stack them if you wish.

It was about 30 minutes before sunset. If the water wasn't so calm, would I have gotten more of that flowing look?

So if I do understand correctly, I would have gotten about an 8sec exposure without the filter at f22?

Well, if it's like the canals around here the water is pretty flat and featureless even though it is flowing. You need some sort of distinct movement over a reasonable distance to get the effect I assume you are after. If the water is always looking in the same place (yes, I know it's flowing slowly but it is flat and at the same level) it will look the same for the whole exposure.

It works for waterfalls because of the tumbling nature of the water as it rushes over rocks and drops, similarly seascapes work because of the action as the water comes and goes with each wave.

Imagine somebody staying in one place and dancing, over a long exposure the whole body, arms and legs will be moving around and will create an image which is mostly extravagant blurs and sweeps and barely recognisable as a person. Now, if that person stands still, with their arms by their sides for the same length exposure, they will be quite clearly seen as a person stood with their arms by their sides. there will be very little blur as they didn't move around enough.

Your canal is the equivalent of the person standing still, you need to find somewhere where the water "dances".

Over the weekend I hope to take some fountain photos.

From what I gather, I just set the aperture to the smallest I can (f22 or higher), and let the camera do the rest? It sounds almost too easy. :/

KirkS518 wrote in post #14448212
It was about 30 minutes before sunset. If the water wasn't so calm, would I have gotten more of that flowing look?

So if I do understand correctly, I would have gotten about an 8sec exposure without the filter at f22?

Yes that is correct, your filter extended your exposure from about 8 seconds without it, to 30 seconds in this instance.

30 seconds is plenty to capture flowing water as a dreamy blur, so long as the water is moving enough. Flat featureless water will always stay pretty flat and featureless no matter how long the exposure.

Thanks. At least I know I'm doing it right. Now to practice and expand.