Is this a good example of when an ND Grad would come in handy?

[Ventureoverland]

Whilst out with the camera today I wanted to try and get some milky water.

Everything was blown out, even when stopped down to F22 and ISO 50.

I then had a brain-wave, put my hand over the top half of the frame for a few seconds and only expose the bit behind my hand for a second. The result is below - I know its not a great image, but the water below where my hand was is (almost) milky, and the sky isnt too blown out. The clearly visible line in the water was the shape of my hand.

Now, the question is this... Is this essentially what an ND Grad does? Im pretty sure it is, obviously it does it in a much more gradual way and the line between light and dark on the filter will be straight!

Only asking as Ive read a lot about them and often get myself confused between Grads and ND Grads.

Thx
Jon


http://www.ventureoverland.com/~pub/Photos/2013-07-25/ND_Grad_Needed.jpg

[ricktas]

an ND grad is graduated, dark to clear. It's purpose is to bring a balance to the dynamic range of the scene so that the sensor can capture detail without overexposing part of the scene. Say a bright sky and dark foreground - you would use an ND grad to darken the sky to 'level out' the brightness of the sky by having the darker part of the ND grad over the sky, leaving the ground with the clear part of the filter.

To get long exposure shots of water etc in a bright environment you can do a few things. One is wait till the sun sets and the dusk starts to take over and try then, or use an straight ND filter (no grad) where the entire filter is darker to darken the entire scene, and thus allow longer exposures and the milky water effect.

ND grads are used to darken either the top or bottom of a scene to balance out light levels across the scene. ND filters are used to reduce light levels across the entire scene. If the scene is proving especially difficult you can use a ND filter and and ND grad filter together (filter stacking), to darken the entire scene and then darken the brightest part even more.

[Ventureoverland]

Thanks for your detailed guide Rick, its now much clearer.

So, given the sun was still up, this particular shot should have used an ND, NOT an ND Grad to obtain the required effect.

Thx
J

[ricktas]

yes..or both ND to darken the whole scene and and ND grad to darken the sky more.