OK, does anyone have this filter? i have an inkling hwulex does.... but anyway, i have a question about it. It's awfully expensive.... what does this do that i can't acheive by stacking two circular polarisers, which is obviously what this is in a slightly more convenient design? i figured if i use 2 slim polarisers like the kenko pro1 ones, they should be roughly the same diameter as the vari-ND. so, where's the roughly $200 advantage? surely it can't be THAT much better quality?
I'm actually using the Lee Filters. system. My ND is the 0.6 hard grad. I guess stacking polars would give the same kind of effect, but you have got the problem of stacked filters and reflection. The best thing about my ND is the grad so I can darken the sky without the rest. I've not used my system much since I got it but gave it some good use in teh forest on my last shoot and I truely love it now.
Basically as it says, it just gives you a variable ND, i personally wouldnt bother and just buy one of the large stop cokin ones and a selection of the smaller stop ones. RE grads i use my almost all the time to good effect, its prolly my most used filter now, i use a cokin p120. These are the interesting NDs from cokin: http://www.bhphotovideo.com/c/product/387089-REG/Cokin_Z155_P155_Neutral_Density_Grey.html ~10 stop i think and http://www.bhphotovideo.com/bnh/controller/home?A=details&Q=&is=REG&O=productlist&sku=387091 ~30 stop (if my maths serves me correctly)
ND grads are used mostly in landscape photography. The sky is generally much brighter then land. You can use a ND grad to reduce the light from the sky. This way you can use an exposure that won't overexpose the sky or underexpose the land. Solid ND filters polorizing filters reduce the amout of light evenly over the whole frame, and You can accomplish some of the same shots using multiple exposures, or multiple conversions of the same RAW file by blending them in photoshop. You may run into problems if something in the photo is moving (swaying branches in the wind) or the difference in exposure is greater then the 3-4 stops that. Also you may start running into noise issues as you increase the exposure in RAW. Here's a link to some info I found useful on the different brands of ND Grad filters out there. I have a tiffen, I really haven't used it much, but thats more due to my lack of motivation to take pictures lately. Here is one shot I got with it. http://www.flickr.com/photos/jgarrido/159229362/If it weren't for the ND grad I wouldn't have been able to use such a slow shutter speed and "smooth" out the water.
um i KNOW what ND, and ND grad filters are used for. my question pertained the the fact that since the vari-ND filter is essentially two circular polarisers stacked, where's the $200 difference in performance compared to, duhhh, 2 stacked (good quality!) circular polarisers?
Sorry I was thinking vari-ND was singh-ray's name for ND grad filters, i see now. Yes you can get the same effect with 2 stacked polarizers, but it's easier to get vinetting as you stack filters. Also as Hwulex said you run into more problems with reflections. You can counter this with higher quality multicoated polarizers which can easily cost over $100 each, so it starts to even out. Also if you have a lens with a barrel that rotates as it focues, you have twice as many filters to readjust.
