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11-08-2010, 08:04 PM   #16
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QuoteOriginally posted by ProgMtl Quote
I've been reading up on the use of ND filters...I'm going to Yosemite over the Thanksgiving holiday and am wanting to get some good waterfall pictures (cotton candy type effect)...I understand the use of the ND filters but don't see much on which X to use (2X, 4X, etc.). The cost of buying all of them is a little steep for me right now (and I'm sure getting all of them may not be necessary). Can someone point me in the right direction as to which one is the best starting point?

When/if you get a ND filter I would be curious to see your results when you get back. I have been thinking about buying one but would like to test or at least see the difference of each step before I purchase.

11-09-2010, 06:25 AM   #17
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Consider using crossed polarizers for your nd filter. Then you can get the exposure you want experimentally:

Stack a linear polarizer in front of a circular polarizer.

Or buy a circular polarizer, remove the element, invert and replace it; then stack the polarizer on a circular polarizer.

When the polarizers are completely crossed there may be a color tint added; don't worry about it - just don't cross them that far.

On the other hand, the completely crossed polarizers may well act as a good IR filter - the reason there's a tint is the polarizing filters usually don't work outside the visible (nb) I just tried to do IR with two polarizers I have on hand - it didn't work well for IR, but the crossed polarizers increased the exposure from 1/500 to 8 sec; a factor of 4000- about 13 stops.


Last edited by newarts; 11-09-2010 at 03:13 PM.
11-09-2010, 06:48 PM   #18
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QuoteOriginally posted by noblepa Quote
If the cotton-candy effect on waterfalls is your primary goal, there is another way to accomplish it, other than with ND filters.

Simply use multiple exposures. As long as you're using a tripod, you should be okay. You didn't mention which camera you are using, but my K10D has multi-exposure capability, and I'm pretty sure that most Pentax cameras after it also had the capability.

You can either use the camera's builtin multi-exposure blending, or simply shoot three or five identical shots and then combine them in post-processing. Since you're shooting on a tripod and nothing in the scene changes, except the "position" of the water, you get the same smooth effect.

And you can adjust speeds to do some HDR as well, killing two birds with one stone.

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