It's not terribly easy to adjust filters behind the lens. You have to remove the lens from the adapter and thread the filter onto the ring mounted inside. Sometimes you get a fingerprint on the filter and have to clean it off before using. It's not an ideal setup. I only bother with this on lenses that can't mount the filter up front because of vignetting or missing filter threads--or for diffusion filters/nets/stockings that look distinctly different behind the lens than in front of it.

Does anyone have any experience using Graduated NDs on top of a fader ND? Any issues with that?

A few things that seems to be a major advantage of the Fader NDs over the stacking things onto, say, a Cokin P filter holder are:

(1) you can get the exposure you want just right, instead of potentially having to change your shutter or aperture because your stacking NDs is off by just a little bit;

(2) you are not staking multiple NDs which can increase the likelihood of color shifting, loss of sharpness, etc; and

(3) if you are doing documentary-type work in which you have to transition from bright areas to dark areas while continuing to roll, fader NDs are much more elegant for doing so.

I really like using a Graduated ND on my Cokin holder, hence I'm curious about Graduated NDs on a Fader.

The color shift really only happens at the blackout end of the Vari - ND range anyway, so it's not that big an issue I've found. And if you need to knock out a bit more light without going into that range, add a small ND behind the Vari -ND.

I do like an ND only for faces though, Polarizers flatten things too much.

I haven't tried that but i imagine Grads would be no different than std ND's.

@mark_the_harp Right, makes sense.

How about advantages / disadvantages of using something like the Copkin P holder with, say, these filters: http://bit.ly/r7S8hf

What about the cheap vari nd filters that you can buy on ebay for like 30$? What do you think? Has anyone tried those?

Some footage shot with the Kood nd's

I very nearly went the Cokin P system route, but with the HiTech filters. I discovered that you can buy them directly from Formatt, and even with the exhange rate, tax, and shipping overseas here to the US, it would be much more affordable than buying them from say B&H or Adorama--as I recall it ended up being something like $60 for a set of ND 0.3, 0.6, 0.9, though I might be wrong.

However, after some waffling, the convenience of a Fader ND, for more run 'n' gun shooting, and not having to fumble with swapping out filters won me over at least for now. I don't know if this is true or not, but I red that the Nature Fader ND's on eBay (http://shop.ebay.com/she-in/m.html?_nkw=ND+Filter) are pretty much identical to the branded LCW Fader ND--maybe, maybe not, but the few things I've heard about them have been pretty positive for the price, and I'm a cheap bastard, so I picked up a 77mm one.

At the moment, I've got my GH2, the 14-42mm kit lens, and a Nikon Nikkor 50mm f/1.8 and 28mm f/2.8, all with 52mm filter thread, but I decided on 77mm as a standard filter thread as a way of future-proofing. I almost went with 62mm instead, but there are a few lenses out there with a 77m thread that I've got my eye on.

In addition to the 52mm->77m step-up ring, I got a 3-stage rubber lens hood, which has an outer filter thread that I attach the Fader ND to, which I think works much better than having the hood attached to the outer rotating filter; instead the hood is attached directly to the lens, with the Fader ND attached to it. The only downside is I can't see the markings on the Fader ND and it's trickier to adjust if I have the hood extended all the way--not a big deal, and nothing that I didn't expect.

I only got it yesterday, and I've only gotten the chance to do some cursory tests, but so far I'm pretty happy with my purchase. I am seeing similar to what I have heard about the LCW Fader ND, with some softness at 50mm, but not overly objectionable to me, especially for video--I'm not sure I would have noticed if I wasn't looking for it. There's also a slight color shift, but again, nothing objectionable--and can easily be white balanced out.

Other than that, the only downside is that if I'm not paying attention to what I'm doing, without any hard stops, I can rotate it beyond the Min or Max settings, where it gets a bit unpredictable, but I believe this is also the cases with higher priced ones, except for the Heliopan.

I admit the whole set up does look a bit silly, with the step-up ring and the oversized lens hood, but it does help make the small camera look a bit more substantial.

As always, your mileage may vary, but so far, I'm pretty happy.

I bought this SLIM Vari - ND and i'm very happy with it. The seller is honest and posts info about possible loss of sharpness over 200mm and possible color shift near max ND. Being ultra slim design it gives opportunity to use hoods and other filters. It's only 7.8mm thick.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230614828112&ssPageName=STRK:MEWNX:IT

I just realised that my fader acts like a polarizer! That's bad, especially for dual-body 3D shooting.

Everbody try yours: hold it up to an LCD screen, and rotate it (the whole filter, not the adjustment ring) - does it gradually block out the LCD light? From the front, and back?

I use a cokin A filter with hoon.
I have a Leicaflex set and the biggest thread is a 55mm from my 135 f2.8 so I don need cokin P
nd0.6 (2 stops) cokin A152
nd1.2 (4 stops) cokin A153

15.39$ each
http://www.bhphotovideo.com/c/product/13996-REG/Cokin_CA152_A152_Gray_Neutral_Density.html

http://www.bhphotovideo.com/c/product/13997-REG/Cokin_CA153_A153_Gray_Neutral_Density.html

There is also a Graduated Neutral density filter that I use on certain locations.
http://www.bhphotovideo.com/c/search?Ntt=cokin+a&N=0&InitialSearch=yes

The use of a 4x4 mattebox for me has no sense in dslr its just to hide the camera an to be more obtrusive.

@skiandbike

It is ok to glot it with pictures. At least two for comparison won't be bad. :-)
Thanks for test.
Do you have different Marumi ND filters?

@Vitaliy looks it will be difficult to put these Marumis on something like a Cokin P holder.