Here's a very good test concerning Polarizers. (other interesting tests also)
http://www.lenstip.com/115.1-article-Polarizing_filters_test.html

I'd like to buy some polarizers(linear and/or circular) and have started to do some research on how to lessen the color shift of DIY Variable-ND ( or any Vari-ND for that matter)

No Blue Shift Here: (for a price)
B+W has a Vari-ND out for $579 ($420 on ebay) no thanks...
https://www.schneideroptics.com/ecommerce/CatalogItemDetail.aspx?CID=466&IID=8088

Here's what they say about their Vari:

"This carefully matched set of filters work in combination to produce a density range from 1-1/3 stop loss to 11 stops of light loss. By selecting the best quality materials, Schneider variable ND offer 11stops (ND3.3) attenuation with no blue color shift at maximum density which is a common problem with inferior and unmatched materials common in lesser variable ND filters."


Finding a couple Old, Used, High Quality, Linear Polarizers will better fit my budget.

Yes, Marumi. Good thinking, their polarizers can be bought at reasonable prices and rate highly.
Will need to look in to their NDs.

If buying new(polarizers), we need to start watching for Fake Marumi's now though(like hoya and b+w) I've seen a few with suspect markings.

Great topic Vitaliy.

I recently picked up a Marumi ND8/0.9 screw-in filter from 2Filter.
http://2filter.com/marumi/MarumiNDfilters.html

I'll be doing sharpness and color shift testing this weekend for a variety of focal lengths and will post my results.

Also have a linear polarizer from Marumi on backorder for general use. Stacking two would make a DIY variable option, but I'm worried about color shifts. http://www.2filter.com/marumi/marumicirpolarizers.html (bottom of page)

The Tiffen variable ND looks promising, but supposedly there was a production issue in the first batch. Much cheaper than Singh Ray, but still not nearly as cheap as a DIY option.

I also use 3 Marumi NDs and a Marumi Macro filter. But clever me I got 52mm thread cause I didn't think I'd need more than that cause it covers my 20mm and 50mm. But then I got Samyang 35mm which has 77mm. LOL

I bought the LCW Fader Mark II.

I like it so far. I got the 62mm so I could use it with my 14-140 and 20mm pancake with a step up ring. Nice setup. :-)

Some people say the LCW Fader adds a greenish tinge, but I haven't seen that happen to any of my footage yet.

I went with the Tiffen Water White IR ND 2.1 from 2filter.com. This filter is new for 2011 and is specially designed for CMOS sensors like the RED and GH2. I see a slight loss of warmth but I consider it quite good for 8 stops of light reduction. Take a look for yourself, the first shot (black SUV) is 1/4000 with No ND, the second shot (white car) is 1/50 with ND. Both ISO 160 f 2.8

Hi dkitsov,
I am also thinking to go for heliopan, could you please tel us more about it?for instance does it effect sharpnes, or does it create any color cast.
I saw it in the shop, it looks like very well made and very well callibrated, but i find price was bit high for me . So i would like to understand hiw happy you are with it.
Thanks

@xsa I am pretty happy with it. It does not seem to affect sharpness as far as the video concerned. It is very well built and while there is a shift in color from no-filter on a lens to Heliopan filter on the lens, there is no shift in color between different degrees of ND. Hope this helps.

Yes, Linear Polarizers work just fine with any m4/3 camera.

Summary of options:

Sorry if this is basic.
Please advise of any mistakes.


1. Coated or Uncoated NDs and Polarizers?
a. Let's not open that can of worms, eh? ... or shall we?

2. Stacking
If we are stacking filters, we'd want to go with the largest filter
we can afford for our choice of lens size

a. to eliminate the need to buy multiple sizes of filters, 'one size fits all' with correct step rings
i.e. use your 77mm filter on a 52mm front threaded lens

b. to eliminate the possibility of vignetting by stacking multiple filters
(unless, of course, you're using your 77mm filters on a 77mm lens, but that means you
purchased those oh-so-inexpensive 82mm filters, right?)


3. Stacking ND filters

a. add number of stops together when stacked
b. image degradation by stacking multiples?
c. Or buy an ND16 instead?

wiki-ped:
stops
ND2 1
ND4 2
ND8 3
ND16 4
ND32 5
ND64 6
ND128 7
ND256 8
ND512 9
ND1024 10
ND2048 11
ND4096 12
ND8192 13

So you'd need to stack an ND2,ND8,and ND16 to match most Dedicated Vari-ND's
at around ND256 (8 Stops)

Is this too many to stack? Seems so.

Anyone have an ND8192 ? :-)


4. Stacking Polarizers (4 to 15 f-stops)

some info: problems of mismatched, cheap polarizers?
http://www.digitalphoton.net/making-a-variable-nd-filter-with-circular-polarizers/

Polarizer Options:

a. (2 circulars, but must reverse the glass on the front circular)
b. (1 circular, 1 linear in front)
c. (2 linears, linears are ok to use on the m4/3 format)

Benefit of having a DIY Vari-ND made from two polarizers,

a. you also have a simple polarizer at your fingertips in addition to the DIY Vari-ND.
b. one fewer thing to carry
c. one less expense


5. Just buy a quality Vari-ND, deal with the color shift with a custom WB and the softness above
200mm

Hey how cool would a Vari ND be mounted behind the lens or built into an adapter? Sounds like a good DIY project.

hmm . . . when I get my FD>M43 I might have to try putting a Variable ND inside it. That would be useful.