ND Filter VS Exposure Compensation

Teamfour

Senior Member
I was shooting a waterfall this week and could not stop down far enough (f22 max) to get a long enough exposure for good water flow effect. Admittedly stupid on my part,I completely forgot about using the exposure compensation. Anyway, what is more effective in this scenario, ND filter or exposure compensation?
 

WayneF

Senior Member
Exposure Compensation won't help your water flow.

The ND filter darkens the image, which you correct with a slower shutter speed, which helps blur your water flow. A lower ISO might do this too, in some degree, unless already low. You correct with a slower shutter speed.

Exposure Compensation simply darkens the target goal for your picture, and the metering leaves it there (dark), no matter what shutter speed you use. It does not then correct.
 
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Teamfour

Senior Member
Thanks Wayne! I already had the ISO at the minimum of 100. I mistakenly thought the exposure control was a form of "electronic ND", if that makes sense.
 

WayneF

Senior Member
The EC can reduce the exposure, as much as the ND filter does, but then with the ND filter, you reduce shutter speed to bring the exposure back up to the desired level.


The goal is to reduce shutter speed, to blur the water more.

You can always stop down the aperture, towards f/22, and it gets dark, and then reduce shutter speed to bring exposure back up.

Or (similarly), you can use the ND filter, and it gets dark, and reduce shutter speed to bring exposure back up.

Or both maybe... for greater range, for slower shutter speed.

But nothing corrects for exposure compensation. It just stays dark.
 

WayneF

Senior Member
Dunno, I guess the Powers That Be have not decided to do it. The Canon G12 does have one built in. The tiny compact sensors are a different story though, cannot stop them down past about f/4 without suffering from diffraction. I'd guess that is the actual reason, not waterfalls. :)
 

PaulPosition

Senior Member
Took me a while to figure out out. Exposure compensation only make sense with auto and semi-auto (Program, Aperture priority, Shutter-speed priority). You're basically telling the camera software "I know what you see but, trust me, it should be darker/lighter". It will then play with speed, aperture and ISO (if auto ISO) to match your request.

In A mode it only changes speed, maybe ISO. In S mode, it will tweak aperture, maybe ISO. In manual it will do nothing BUT showing you a different target on the viewfinder's light meter.
 
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