ND Filter

[CowgirlMama]

Is it possible to make an ND filter? I have one, but I have a long distance friend who needs one and wondered if it was possible to make one. The only instructions I've been able to locate require polarizing filters to use together or something along those lines. Is it possible to make one until she can get her hands on a real one or is she just out of luck?

 

[usayit]

In a pinch, I"ve used sunglasses.

As you already discovered, two polarizing filters back to back will make a variable ND filter of sorts.

 

[CouncilmanDoug]

Wel there's welding glass

 

[Buckster]

In a pinch, I"ve used sunglasses.

As you already discovered, two polarizing filters back to back will make a variable ND filter of sorts.

Unless they're circular polarizers, which will not do that. Only the linear polarizers stacked together make a variable ND.

 

[usayit]

I've been told that too... but in a pinch I did use two circular polarizers and it worked fine. Once you get down a lot of stops, I started to get some color casts though. I have yet to prove or disprove that statement.

 

[Buckster]

I've been told that too... but in a pinch I did use two circular polarizers and it worked fine. Once you get down a lot of stops, I started to get some color casts though. I have yet to prove or disprove that statement.

You're mistaken. Possibly you were using linear polarizers and didn't realize it.

I have 4 CPs here, and I can confirm without a single shred of doubt: Stacking and rotating any two of them does not produce a variable ND effect in any way. There is no change at all as they are rotated against each other.

I also have some sheet linear polarizing filter material here. It DOES make a variable ND when two pieces of it are stacked and rotated against each other.

 

[usayit]

Hmm interesting.... maybe my memory is not serving me correctly. You've peaked my curiosity now...

Did you try it back to back?

I am pretty sure they are circular... they were used with autofocus cameras. In fact, I popped the glass out of one and put it into a UV filter ring that had cracked and screwed into the back of a circular polarizer. I used the DIY variable ND filter for a few years until I decided that a collection of ND filters + step up rings was better suited. (The polarizers I used where cheap too) As I mentioned as you get darker, you end up with a color caste.

PS> found the an old thread that was being discussed. HelenB (as always) was very helpful in describing in detail. I found out through word of mouth at a camera swap and figured out through trial and error. I still have the filter sitting in a bin.. I could dig it out and make more test shots.

http://www.thephotoforum.com/forum/...olarizing-filters-one-variable-nd-filter.html

 

[Dao]

I remembered I tried a pair of polarized sun glasses and it act like a grad ND. ( have not tried it as a photography filter, of course)

 

[tirediron]

*Steers the thread back on topic...* OP: You really can't make an ND filter, but as mentioned, there are lots of things that you can use, such as sun-glasses, welding-filters, etc, all of which will have slightly different effects. As long as you and/or your friend are in a location served by either postal or courier service, there's always eBay...

 

[Buckster]

Did you try it back to back?

I probably only screwed them together, straight up. I'll have to try flipping one backwards and see what happens. I'm guessing that between what you and Helen said, it should work.

Much appreciated on the clarification! I stand corrected! :thumbup:

 

[usayit]

Oh forgot another suggestion I've heard tossed around...

Stretched pantyhose.... er... never tried it myself as the chances of me having an ND filter in pocket is a lot higher than pantyhose...

 

[zamanakhan]

In a pinch, I"ve used sunglasses.

As you already discovered, two polarizing filters back to back will make a variable ND filter of sorts.

Unless they're circular polarizers, which will not do that. Only the linear polarizers stacked together make a variable ND.

you need to flip one of the cpls, it works best if you have a uv or a cheap filter that stays still and flip the cpl into it, then mount the cpl on to that.

Actually let me know how that works... if its comparible to the higher end variable filters i may get another heliopan or hoya cpl and throw it in a reversed uv filter ring. I can keep that for a quick variable nd filter along with a 10 stop filter.

 

[Buckster]

Confirmed.

I used two B+W F-Pro MRC 77mm circular polarizers.

Stacked naturally with the threads both facing the same way, turning them on each other changed color temperature slightly from cool to warm and back.

Stacked with the threads facing each other, turning them did nothing at all.

Stacked with their outer rings facing each other, turning them produced a variable ND filter that appeared to give about 7-8 stops of variation, per my camera's meter.

Thanks again, usayit, for getting me straight on this!

 

[zamanakhan]

Confirmed.

I used two B+W F-Pro MRC 77mm circular polarizers.

Stacked naturally with the threads both facing the same way, turning them on each other changed color temperature slightly from cool to warm and back.

Stacked with the threads facing each other, turning them did nothing at all.

Stacked with their outer rings facing each other, turning them produced a variable ND filter that appeared to give about 7-8 stops of variation, per my camera's meter.

Thanks again, usayit, for getting me straight on this!

7-8? not like the traditional 2-8?

How was the quality of the effect themselves? worth getting a variable filter over two cpl's? i ask because my current heliopan has a scratch on it and i wouldn't mind getting another cpl.

 

[Buckster]

Confirmed.

I used two B+W F-Pro MRC 77mm circular polarizers.

Stacked naturally with the threads both facing the same way, turning them on each other changed color temperature slightly from cool to warm and back.

Stacked with the threads facing each other, turning them did nothing at all.

Stacked with their outer rings facing each other, turning them produced a variable ND filter that appeared to give about 7-8 stops of variation, per my camera's meter.

Thanks again, usayit, for getting me straight on this!

7-8? not like the traditional 2-8?

I'm saying UP TO about 7 to 8 stops of variation total. That was based on just counting stops from "wide open" to "closed down as far as possible"; There were a total of 7 to 8 stops in that range.

How was the quality of the effect themselves? worth getting a variable filter over two cpl's? i ask because my current heliopan has a scratch on it and i wouldn't mind getting another cpl.

I don't have a variable ND to compare it to, so I couldn't tell you how they compare. I don't know how to define or quantify the "quality of the effect themselves". You turn it, the whole scene gets darker in the viewfinder as you do.