Cheaper Alternative To Singh Ray Variable Neutral Density Filter

[princer7]

The price of Singh Ray's Vari ND filter was too much for my wallet to spend on a single filter. I really liked the idea, however, of being able to dial in the level of filtration. After doing some reading online, it was mentioned that you can use two linear (for film) or a linear and circular polarizing filter (for digital) and get the same results.

I purchased a few weeks back a Slim mount 77mm B+W Kaesemann circular polarizing filter. Through Adorama last week, I found a used B+W linear polarizing filter for @ $40. The circular polarizing filter is doing double duty as I needed one of them anyway. For $40 I get the benefit of having the entire range of neutral density filters in one. http://www.texasphotoforum.com/forum/images/smilies/biggrin.gif

I gave this a try this evening when the linear filter arrived. Works great with no noticable decrease in image quality. The linear filter mounts to the camera lens with the circular filter on top. Cannot wait to give it a full run through tomorrow outside.

[jrsforums]

I would be interested in the results of your set up. My initial impression is that you have the lenses backwards...at least from what I understand.

The CPs, vs. linear polarizers, are recommend because auto focus has a problem with polarized light. Therefore, they add to the back (lens side) of a linear polarizer an add'l film (filter) which "twists" the polarized light so it will work with the AF system.

If you pus the LP between the CP and the lens, the "twisted" light will be polarized by the LP, causing whatever problems the CP is designed to avoid.

I think you need to mount the CP, then place the LP on it.

I have thought of trying this, but never got to it. It will be nice to hear you prove or disprove what I said above. I also would be interested in how easy it is operationally...i.e. turning the LP on the turnable CP. I also hope you have some lens wrenches in case they are difficult to separate.

[Double Negative]

I'm very curious as to how this works out for you as well... I too have thought about the Vari-ND filter and even being used to high prices as I buy Heliopan... This one is a bit much.

Besides, I don't want to add a whole horde of ND filters to my bag, it's heavy enough as it is. Simple, cheap and light is good.

[DavidW]

I'm with John - I think princer7's setup is backwards. The variable ND has to be two stacked polarisers - I can't think of any other way it would work.

However, you want the quarter wave plate closest to the lens so as no plane polarised light can enter the camera - in other words, you want lens - circular polariser - linear polariser.

I'm trying to think whether or not it would work with two stacked circular polarisers (like princer7, my main circular polariser is a slim mount one - in my case because I own an EF 16-35mm f/2.8L and may go full frame in the future). If I had access to another 77mm circular polariser, I could experiment - but I only have one and acquiring another involves non-trivial expense.



David

[princer7]

Seems I am on the hunt for a regular circular polarizer to test with. :confused: I apreciate everyone setting me straight. :D

[jrsforums]

DavidW...

Good idea, but... I just tried 2 CPs. Got slightly darker with rotation, but not much. I guess the 1/4 wave unpolarizes it enough to destroy the desired effect.

BTW...it was not easy to keep the inner CP from turning while turning the front one (of course they were slims). Definitely a tripod only solution. Plus, I am still scared of getting them too snug. My gut says to stay with my 8x ND.