Any issues re: linear vs. circular polarizers?
 

Curious to know if anyone can tell me if a linear polarizing filter (compared to a "circular polarizing filter") interferes with auto-focus on the EX1. Since I don't understand the exact mechanism used to achieve auto-focus on this camera, I am unwilling to guess. Mind you, if it does mess up auto-focus, that's not the end of the world for most purposes, but I want to know regardless before choosing a $200 or $300 filter.

according to Ryan at Schneider you can use linear polas on any DV camera while using auto-focus.

Hello Jim,

I had the same questions that you express. You´ll find all the answers I got under the thread "Circular polarizer with the Sony EX-3". Go linear seems to be sum up...

-terje

It may be because of the CMOS sensors, but I've found I have to use circular polarizers (not linear) on the EX1 or I get color shifts when rotating the filter. Does not matter on my Z1U (3CCD) or Panasonic DVC-Pro camera.

Hello Ronn,

Color shifts when rotating filter? Really? Maybe we can get Ryan at Schneider to comment on this? Ryan, can you elaborate? Thank you.

-terje

Ryan already has...

http://www.dvinfo.net/conf/sony-xdca...ges-color.html
I can post some stills showing linear vs circular on same camera.

Here's what George Strother said in http://www.dvinfo.net/conf/sony-xdca...ecipes-22.html :

Tested the Schneider circular Tru-Pol. Rotation makes no measurable color shift. White balance shifts about 3% toward cyan when mounting the filter. Need to re-white when the filter goes on or off. Panning with the circular does not color shift.

Tested a Tiffen linear polarizer. 90 degree rotation gives a 30% shift magenta to green! Optimize the polarization, white balance and pan 90 degrees can give a 30% green shift. Not good. Mounting it backwards made no improvement.

Neither filter blocked the auto focus system.

It doesn't take scopes and test charts to see this color shift. Just watch on the LCD screen as you rotate the filter or make a long pan in sunlight. Maybe someone can test other brands of circular polarizers and post here.

As I have discussed recently on another thread. Our tests show no color shifts with the EX1 and Tru-Pol. However, others have experienced it. Always re-white balance and the issue that may exist on some cameras will be solved.

Ryan Avery
Schneider Optics

New data on Polarizer color shift
 

Doug Jensen, of Vortex Media ("Mastering the PMW-EX1" & "Mastering the PMW-EX3") recently sent the following to me via email (and to Avery at Schneider Optics) regarding his findings. I thought it imperative I share with the forum, if only to help some folks avoid the same frustrations:

----------------------------------------------------------------------

I came across both of the threads about color-shifts while using polarizers with the EX1 and EX3 and I thought I'd let you know what I found out after some testing.
I hope you don't mind me contacting you directly.

I have experienced the color shifting phenomena myself so I decided it was time to get it fixed. I have two 4x4 Schneider True-Pol filters and they are NOT the same. My testing shows that you DO need a circular polarizer with the EX1 and EX3.

Filter #1 was purchased in 2001and the printing on the glass says "Schneider B+W True-Pol"
Filter #2 was purchased last week from B&H and the printing on the glass says "Schneider THIS SIDE OUT Circular True-Pol"


Filter #1 causes a serious color-shift when rotated no matter which direction it is facing in the matte box.
Filter #2 does not cause a color shift as long as the glass is facing the proper direction. If the filter is mounted in the wrong direction then there is some color shifting, but not as severe as with Filter #1.

I tested both filters with my EX1 and my EX3 and as far as I can tell there is no difference at all between the two models of cameras. In other words, just as I knew they would, the EX1 and the EX3 react to the same way to both filters.

So, my recommendation to anyone looking to buy a polarizer to use with the EX1 or EX3 is that you must get a Circular Polarizer. Yes, there is a difference and it is plainly visible right on the camera's LCD -- no scopes are necessary.

I hope that helps shed some light on the debate and I only wish I had discovered this information in time to include on my DVDs. Damn!!
Feel free to pass along my testing on DVi if you would like to.

Right - Linear Polarizers do not work
 

Thanks Doug and Ronn, Wish I would have known this before I ordered the B&W top linear Polarizer MRC 77mm screw on filter 2 weeks ago. Seemed to be the ticket after reading all the forums. I even tried reversing the filter and same results - color shifts from Magenta to cyan. The attached photos are examples of just turning the filter 180 degrees. Same results shooting 3 different days. Fortunately, I bought it at B & H photo and will exchange for a circular type.

Ok, so I did some further testing on a new EX1 and EX3 (we own an old prototype). I was able to replicate the problem. After some fishing around in theory and from testing this is what I found.

All beam splitting prisms in all video cameras create some level of polarization of the light that is reflected from the prisms. Generally this is extremely minimal and therefore not an issue. A linear polarizer will cross polarize with any other polarized light such as the light reflected from a prism in a video camera. This could cause color shift (either warmer or cooler) because the red and blue channel are polarized while the green channel is not. A circular polarizer will not cause this problem because it does not create the cross polarization. If the color shift is only at the edges of the frame then there is a phenomenon known as "color shading" that is occuring and this is another kettle of fish altogether which requires further image analysis to discover the cause.

The Sony EX1 and EX3 obviously have some greater level of polarization reflected off of the beam spliter and therefore causing cross polarization of the blue and red channels. I have maintained for sometime now that virtually all video cameras do not have this greater level of polarization off of the beam splitter and therefore a linear will work just fine. We can now modify that to say that there may be a few out there that polarize more than others and therefore a circular polarizer should be used. As I have always said, if you want to be safe use a circular but you most likely will not need it; unless you own a Sony EX camera.

Ryan Avery
Schneider Optics

Ryan, After following your recommendation a few weeks ago (I refer to my thread about using a circular polarizer on the EX-3) I ended up buying the Schneider True Pol 4x4 Linear polarizer, even if I initially was set for a circular polarizer. You were quite clear in your recommendation, and now I understand that you´ve come to another conclusion when it comes to the EX-cameras? I understand that things evolve and change, but it´s vital that the info you, as a "filter professional", kindly share, is based on actual tests. Your expertise is very valuable for all of us here on the forum. You provide info that we can trust. I really would like to continue to do so.

Best,
-terje

Linear polas out for EX?
 

After reading through this thread, I was keen to try out my polas on my new EX3. I have a shoot coming up next week in the Nevada desert and realized if my polas don't work I'm in trouble..... I did not have a clue that there might be an issue until discovering this thread just last night.

So, here's what I found.... to no surprise to the previous testers.... linear polarizers are out for the EX3.

I used a brand-new Schneider Tru-Pol (linear) 4x4 both ways, and the same result: hideous color shifts.
I used two older Schneider polarizers, (one Tru-Pol, one a warm polarizer) both 4x4, both linear, and.... no surprise. Same result. Both ways.
I used a really old Tiffen Series 9 polarizer (from my local TV news days)... not sure if it is linear or circular.... but same result. There is only one way to put the series 9 on, so I couldn't try it both ways. I suspect it's linear, since the result was the same.

I really wish I'd seen this thread earlier, so I could have ordered a new circular 4x4 in time! Now it's sunday, and I have to leave for my shoot.... guess I'll just have to white balance continually to correct for the color shift.

I have used these Tru-Pols on Betacams and XDCams (HD) with no problem. I have also used them on a variety of DV and HDV cams with no problem.... this was the first time I have ever seen this effect. So, I guess to all the EX1 and EX3 users out there... time to be shopping for a new polarizer.

Terje,

My initial comments were based on theory and a record of 100% HDV cameras in the past not having this problem. It could be a trend for Sony to continue to use this type of prism in the future causing this problem but I doubt it since the Z7U and the FX1000 have been tested without these problems.

Ryan Avery
Schneider Optics

Not to beat a dead horse, Ryan, but what you SAID (12/26) was "Always re-white balance and the issue that may exist on some cameras will be solved."

That's really not true, as even you now know. I guess what we have all learned is not to take anyone's "theory" too seriously if it's not supported with empirical knowledge. Especially when using that info to decide on an expensive purchase.

Point well taken. This is the fact of all forums is that we need to listen to each other. I use these forums to educate people on filters. What I get back is testing and info that I otherwise would not have known because I don't have time to test our filters on everything out there on the market (I don't even have time to read in the B&H catalog on everything in the market!).

I appreciate your input and I hope we all can look into issues like this in the future with an open mind and especially the real testing.

Ronn, I also look forward to seeing your DVDs.

Ryan Avery
Schneider Optics