Double linear polarizer

Leonardo

For awhile I'm thinking about purchasing ND filters. Then I've found this:

"Two linear polarizers in twin rotating mounts permits steplessly variable light reduction up to EV -10.0, without any effect on color."

Then there is a fact that linear polarizer is for use with cameras without a beam splitter, i.e. cameras with metering behind or on the mirror and AF cameras. And that's because if a linear polarizer is used various errors may occur in metering and, with AF cameras, focusing. In addition vewfinder information may not be visible.

Now , question is, what if someone decide to neglect all these warnings, what to expect in practice? Plug and play or plug and cry?

z_28

What's warnings ?

That one ?
"Two linear polarizers in twin rotating mounts permits steplessly variable light reduction up to EV -10.0, without any effect on color."

That's ridiculous.

Two 100% effective polarizers rotated 90 deg between each other -
should cut 100% of light !!!

Since nature isn't perfect some light will go through,
cheaper filter - more light

Anyway with two polarizers all you receive will be expensive way to replace one ordinary ND filter !

cmason

believe he is referring to the warnings to not use Linear polarizers but instead circular polarizers with dSLRs/auto focus cameras

Leonardo

z_28 wrote:

What's warnings ?
That's ridiculous.

Two 100% effective polarizers rotated 90 deg between each other -
should cut 100% of light !!!

Since nature isn't perfect some light will go through,
cheaper filter - more light

Anyway with two polarizers all you receive will be expensive way to replace one ordinary ND filter !

I did not want to start theoretical debate but experience at first hand about use of two linear polarizers in twin rotating mounts and its effect on dSLR cameras.:D Or maybe I'm on wrong place, or even mistaken about this forum as "digital grin" to ask question and receive underestimating answersD

Expensive way.....? I think I'll use my "camera obscura" over again

:]

hgernhardtjr

z_28 wrote:

Anyway with two polarizers all you receive will be expensive way to replace one ordinary ND filter !

Not so, Z_28. I've used a "doubled polarizer" many times with SLRs over the past umpteen years and in full manual with dSLRs. As you rotate the outside ring, the image gets darker or lighter ... in effect it is a variable ND filter up to 10 (or sometimes greater).

Leonardo, if you can actually try one whilst shooting out the photo-store's door or window, you could see if it will function with your camera in full auto mode. On my Canons it is a 50/50 proposition, which is why I only use full manual settings when I use it (nowdays rarely ... although I do use an ND 400 filter to play around with loooong exposures (nifty, anything walking/driving through a scene vanishes) or IR from time to time).

Leonardo

hgernhardtjr wrote:

Not so, Z_28. I've used a "doubled polarizer" many times with SLRs over the past umpteen years and in full manual with dSLRs. As you rotate the outside ring, the image gets darker or lighter ... in effect it is a variable ND filter up to 10 (or sometimes greater).

Leonardo, if you can actually try one whilst shooting out the photo-store's door or window, you could see if it will function with your camera in full auto mode. On my Canons it is a 50/50 proposition, which is why I only use full manual settings when I use it (nowdays rarely ... although I do use an ND 400 filter to play around with loooong exposures (nifty, anything walking/driving through a scene vanishes) or IR from time to time).

Thank you very much for advice. I just wonder how this works on dSLRs, is it usable in manual focusing and metering, so I guess it is usable with full manual mode I prefer to use (except MF )

gryphonslair99

If your looking for a varible Neutral Density filter this sounds like the trick to me. Althouh it's a touch pricey.

http://www.singh-ray.com/varind.html

Scott_Quier

I was talking to a lady with a PhD in optic who also happens to be a photographer about this vary topic. According to her, if you mount a CP to your lens and then an LP to the CP, you will get the variable ND filter effect withou loosing your capability to autofocus, etc.

Does this actually work? I don't know. But according to her, the CP will re-polorize the light in a fashion that the camera can use.

Something for someone with one of each to give a try.

Leonardo

gryphonslair99 wrote:

If your looking for a varible Neutral Density filter this sounds like the trick to me. Althouh it's a touch pricey.

http://www.singh-ray.com/varind.html

This is helpful. Thanks for link.

Joves

I use an 8.0 ND on occasion and, hve stacked my CP on it to get even darker with good results. I used to get them in diffrent densities back in the old days and, stack them. But Im in N.Az and I was lucky to find the one I have.

claudermilk

Scott_Quier wrote:

I was talking to a lady with a PhD in optic who also happens to be a photographer about this vary topic. According to her, if you mount a CP to your lens and then an LP to the CP, you will get the variable ND filter effect withou loosing your capability to autofocus, etc.

Does this actually work? I don't know. But according to her, the CP will re-polorize the light in a fashion that the camera can use.

Something for someone with one of each to give a try.

Isn't that precisely what the linked Singh-Ray variable ND filter is?