UKC

Will need to be 77mm for my largest lens...but not sure what strength to go for.

I want to take silky waterfalls...not necessarily in bright daylight (though might be nice) but more in evening or twilight. Also want to get pictures of the beach/sea at sunset with silky water.

I am looking at an ND64 Hoya pro-1...82mm thread for £60 (82mm cause is cheaper than 77mm lol).

Would this be appropriate?

Thanks for any help!

In reply to phja:

Try a grad kit. Will enable the features below the light line to stand out also. Ive got

http://www.amazon.co.uk/Cokin-H250A-ND-Grad-Kit/dp/B000A40M22

and used it on my landscape/waterfall/sunset shots.

In reply to phja:
In all honesty, if you want that 'milky' effect then I would suggest a 'Big stopper' (Google it) which is a 10X ND filter that can be used for both colour and B&W photography. They are great (I have one).
The only drawback is you need the filter holder etc and the 10X filter itself will set you back best part of £100 AND..... it's made of glass !! so no dropping it
The one I have is made by LEE filters, but you may be able to find a cheaper alternative ??
Good luck, you can get some great effects with it
JH.

In reply to phja:
If you really want to take your photography forward, I'd just stump up the cash and get a Lee filter holder system, and a .9 ND hard grad, possibly available as a kit. With that grad filter, you can use it as a full .9 ND filter, or use it as grad and reduce the light for part of the frame.
I bought into the Lee system very early on, and have never regretted it.

The filter you have mentioned would be suitable, you may want to also consider the B+W 10 stop filter or even a variable fader one (Light Craft Workshop produce one of these). I would not recommend the 0.9 Grad ND for the application you mentioned in the OP. I picked my 77mm B+W 10 Stop ND filter up from eBay for under £50 I seem to remember.

I use graduated filters a lot for landscape work, the size I have (Cokin P) does not quite cover the entire frame enough to use it as a replacement for a solid ND filter. This will depend on how wide of an angle lens you have, the softness/hardness of the graduation and the brand you choose to get. I was using a 10mm lens on a crop sensor camera with a HiTech Hard Grad.

To get the silky water motion in waterfall I use either a 10 Stop B+W filter or a 3 stop Hoya filter depending of the brightness and speed of the water. For beach shots I will use both a solid ND filter and a graduated filter on the sky as this will generally be brighter.

What lens / camera are you using? I would say that graduated filters are extremely useful and I use them a lot more than the solid ones, however hard edge grad filters are generally (IMHO) less useful and one 3 stop filter may not reduce the shutter speed down to what you want to.

In reply to phja:

http://www.diyphotography.net/use-welding-glass-as-10-stops-nd-filter