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Old March 16th, 2009, 06:31 PM   #1
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Circ and Lin polarizer to adjust light

Curious if any of you guys with the MKII have tried using a circ polorizor combined with another polarizer to create a variable ND filter and control how much light you have coming in? It seems it could provide a little flexibility around all the auto functions to achieve desired shutter speed & aperature combination for different lighting situations.
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Old March 16th, 2009, 09:20 PM   #2
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Soon as I get a chance I'm going to be testing this one out...

Singh-Ray Vari-N-Duo Polarizing Variable Neutral Density Filter
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Old March 17th, 2009, 01:28 PM   #3
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Yes I am using a circular polariser behind a linear polariser (both Hoya) to act as a variable ND. A blue colour cast is introduced, which increases as you stop down - so you have to keep an eye on your white balance.
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Old March 17th, 2009, 05:03 PM   #4
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I use 2 77mm Hoya HMC slim circular polarisers, one reversed. Works well , there is a colour shift but its not too bad.

I'm planning to try using 2 Schneider 4x4 Circular polarizers in my new Mattebox, I'll let you know if it works.

Dan
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Old March 17th, 2009, 05:08 PM   #5
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Cir and Lin Polarizer To Adjust Light

The link for Singh-Ray 8 stop Variable ND filter may be of interest.

I'm pleased with results so far, easy to adjust after a little practice.

Andrew Yip Nature Photography Using a variable ND filter with the 5D Mark IIís video mode
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Old March 17th, 2009, 06:52 PM   #6
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I've been watching the MKII since being introduced and am trying to decide if I should wait until the MKIII or IIb.... with manual controls comes out. I currently use an XHA1, but the MKII footage looks phenominal but sounds like its a real hassle to match shots and work around the controls. Using opposing polarizers or variable ND's would seem to help a little.

What do you guys think that have it, wait or jump in?
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Old March 17th, 2009, 08:15 PM   #7
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Just came in from outside testing the Singh-Ray Vari-N-Duo Polarizing Variable Neutral Density Filter.... works just like the website Mr Coker posted as to being able to control
the parameters of the camera...

the main issue is too much light will cause the camera to close down the aperture when your looking to get short DOP... the ND has variable 8 stops of adjustment.. this makes the camera open the aperture and you get to adjust your DOP in bright sunlight as you want...

The one I have also has the included polarizer...

the package works well... its a little tricky adjusting the ND portion and then having to
go back and adjust the polarizer without messing each other up... but its doable.

I know it works on video... can't wait to try it out on stills...

I saw no color shift problems except the richer colors that I would have expected with the polarizer portion of the filter.

I also made a list of all my lens filter diameters... then I also ordered a couple of step
down rings so I can put the filter on most of my lenses...

also of note... this filter is pretty thick... so it does not work on super wide angle lenses...
I could see the filter edges thru the lens when mounted on the 24-105 at the 24mm setting... zooming in a little did the trick with that lens...
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Old March 17th, 2009, 08:22 PM   #8
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Quote:
Originally Posted by Roger Shealy View Post
I've been watching the MKII since being introduced and am trying to decide if I should wait until the MKIII or IIb.... with manual controls comes out. I currently use an XHA1, but the MKII footage looks phenominal but sounds like its a real hassle to match shots and work around the controls. Using opposing polarizers or variable ND's would seem to help a little.

What do you guys think that have it, wait or jump in?
I'd say jump in and have some fun with it... the weather is getting ready to cooperate soon..
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Old March 18th, 2009, 10:28 AM   #9
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Since the 5D2 only uses a couple of f-stops anyway, I'd be way more tempted to just buy a couple of standard NDs and scrap the whole vari-ND thing myself. I mean indoors, you're fine with nothing. So, I'm thinking you only really need one to knock down an overcast day or when in the shadows (maybe a .9 or 1.2?), and another to knock down being out in the bright sun (1.8?). Alternatively you could stack, but my instinct is to try to avoid that.

Anyone have any thoughts on what might be a good combination of standard NDs?
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Old March 18th, 2009, 10:43 AM   #10
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It also depends on the speed of your lens.... I have always had to use a polarizer on
my 1.8 lens when outdoors in bright light....
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Old March 18th, 2009, 11:19 AM   #11
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I can help a bit with this discussion. A "variable ND" is really two linear polarizers. When you cross two linear polarizers you get cross polarization which blocks light. If you mount the polarizers in a precise fashion and measure the light blocked on a densitometer then you can arrive at some optical density which loosely relates to what an ND filter does.

The major downside to crossing two linear polarizers is that you will create a slight color shift in the image which will need a separate white balance with each change in light loss. Also, the chances for color fringing increase substantially.

For the DIY crowd out there; you cannot get cross polarization with two circular polarizers or even one circular polarizer. Circular polarizers feature a 1/4 wave retarder that prevents cross polarization. This is important to the metering and focusing properly functioning on your camera.

The 5D MKII is an SLR camera which uses prisms to focus as well as assist the complex metering system. A circular polarizer is required to prevent viewfinder black-out and metering issues so this type of home made variable ND wouldn't work too well.

Ryan Avery
Schneider Optics
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Old March 18th, 2009, 12:35 PM   #12
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Ryan,

I think you are missing the point with this camera, we are not using AF or metering with the 5dmkII camera in video mode. That's why 2 circular polarisers works well, in fact I was intending to buy 2 of your circular polarisers so if you know of any other reason why not to then please let me know asap. This method has far less colour shift than the linear polarisers I've tried.

I am already happily getting a variable ND effect with 2 hoya circular polarisers, with one reversed. I believe many others are too, is there some reason this wouldn't work well with Century filters made of Schneider glass?

Dan
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Old March 22nd, 2009, 11:27 PM   #13
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Ryan,

Any thought??? I would really like to order your filters.

Dan
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Old March 23rd, 2009, 01:15 PM   #14
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Hi, Dan. Are you satisfied with the footage you're getting from the two circular Hoyas? And are you just changing brands because you are moving to 4x4 square filters?

I already have an 82 mm Hoya HMC circular pola which has looked fine when I've used it. It has front threads, so I can get another pola on the front, but I'm confused when you say you have one of your polas reversed. How would that work, since I presume you'd have two female threads facing each other?
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Old March 23rd, 2009, 08:38 PM   #15
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Elizabeth,

I dismantled one of the Hoya filters and reversed the polariser. I'm satisfied with the Hoyas but even using thin mounts I have problems with cut off for ultra wide lenses. I just bought a new Genus 4x4 mattebox that amazingly allows wide angle use of square filters so I'm going the 4x4 route for everything now.

Dan
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