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Old Aug 23, 2018, 12:31 PM   #1
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Default ND Filters

I want to use a ND filter to blur water and generally play about. How and when do I focus, do I use AF or MF. All comments welcome
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Old Aug 23, 2018, 1:44 PM   #2
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Neutral Density Filters limit the amount of light that passes through the lens to the sensor. As such, they require that, in order to maintain a proper exposure, you use a correspondingly longer shutter speed. For instance, if your composition requires an exposure of f/6.3, ISO 100, and a shutter speed of 1/2000 second, if you inserted an ND 0.6 filter, you'd need to increase the exposure time to 1/500 second. In so doing, you'd preserve the depth of field because the aperture hasn't changed, but increased the exposure time and correspondingly the motion blur of anything moving within the composition.
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Old Aug 23, 2018, 3:22 PM   #3
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If you are attempting to get the very soft waterfall effect, you will probably need a s/s of 1 or 2 seconds, so a tripod is a necessity. Not being a fan of the look, I haven't done this, but my guess would be that you would focus and meter manually before putting on the filter, then change the exposure based on the density of the filter.

I believe there are also photo editing programs which can give a similar effect by adding multiple frames without over exposing the result.
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Old Aug 23, 2018, 8:04 PM   #4
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Here's an image showing the effects of different shutter speeds on an image of a stream:

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Old Aug 29, 2018, 6:14 PM   #5
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Quote:
Originally Posted by SteadyEddie44 View Post
I want to use a ND filter to blur water and generally play about. How and when do I focus, do I use AF or MF. All comments welcome
G'day mate

I note also that this is your Post #1 on this forum - so welcome and let's find a bit more about you and your photography

By adding a ND filter to the camera all you are doing is pretending day-time into night-time ... and the camera's focus & meter departments WILL look after things quite okay

Use a low ISO [80 or 100] & also a small Aperture [F11 to F22] and a tripod ... and get close to the water / movement to make sure it comes out 'real blurry'

Hope this helps
Phil
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Old Sep 17, 2018, 12:54 PM   #6
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Quote:
Originally Posted by SteadyEddie44 View Post
I want to use a ND filter to blur water and generally play about. How and when do I focus, do I use AF or MF. All comments welcome
I think the easiest way for a beginner to do this is frame and compose from a tripod in Aperture mode, then use AF lock. "Then" add the ND and the camera should automatically compensate with shutter speed if you have the ISO locked.

At some point you might have to use Manual mode and do everything manually.

Long exposures are time consuming anyway, so doing back to back shots for comparison is routine. You might use several NDs, so you don't want anything to change from shot to shot except for the shutter speed.
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Old Sep 17, 2018, 3:42 PM   #7
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Another thing you might try is bracketing the shutter speed, so you have a variety of images to choose from.
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