ND filter shutter speed conversion

Started 5 months ago | Discussions thread
Rodger in Edmonton
Rodger in Edmonton Veteran Member • Posts: 3,663
Re: ND filter shutter speed conversion
1

BBbuilder467 wrote:

Merlin5 wrote:

BBbuilder467 wrote:

Merlin5 wrote:

Hi guys. I'm going to be buying a 10 stop ND filter and have been learning how to expose for it from a youtube tutorial.

In the tutorial he shows a conversion chart so that if for instance he's correctly exposed at shutter speed 1/1000th and ISO 100 before putting the filter on, it'll be 1 second when the filter is put on. Or if it's a different aperture and correctly exposed at1/250th, it'll be 4 seconds with the filter on. Why would I need a conversion chart though if presumably all I have to do is keep dialling the shutter speed down until I see the exposure meter correctly exposing, i.e, in the centre?

For long exposures, you'll be using a tripod and Manual Exposure mode. Adjust the exposure to "0" or whatever you want for that scene. Then, add the ND and adjust the shutter speed back to the the same EV. You don't have to calculate anything. Except for motion blur or a little contrast, the before and after are identical. All that changes is shutter speed.

Thanks BB builder. With a circular screw on ND filter, it should be possible I can smooth out sky and water in a single long exposure, as long as any visible clouds are moving quite fast?

It doesn't take much to blur water, but clouds can take minutes. They don't always move fast or in the right direction.

Following up on BB'c comments I have this 30s vs 88 s exposure to illustrate the effect - the water in the 30s has a pretty nice glass effect but the clouds are totally meh.

The second was much more to my mind's eye goal of the desired motion blur.

These were done with the Lee Big Stopper - 10 stop ND

* I know the EXIF tag says 30s but this is incorrect, I checked the RAW metadata twice and they are both 80s plus in duration.

88s river scene

My river and surrounding has little whitewater - I have to go to a reasonably big sized lake on a real windy day to get the beautiful white fog effect around the dock.

One thing that really helps is use the online weather tools and wait out the weather - here is another one from a bigger cloud movement day.

The best days are high cloud movement with low surface winds.

81s urban scene

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Best Regards, Rodger
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