# Interesting ND filter, Anyone tried?



## Manlatiger (Jan 23, 2009)

Dear all,

I found this interesting ND filter in Ebay, seems to be a new product.
Did anyone tried with this? I'm Planning to get one.

Fader ND Filter (from ND2 to ND400) 77mm - eBay (item 140296353178 end time Jan-28-09 00:21:40 PST)

Cheers


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## Pure (Jan 23, 2009)

Judging by the crappy English, and it's from china, it's probably low quality glass with a even crappier coating.


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## dEARlEADER (Jan 23, 2009)

i especially enjoyed the "high quality professional photography" seal of endorsement on the add...

$200 bones??

i dunno.... it's unproven....

i'd rather waste my money on the more affordable cokin p series....

if you buy it let us know how it works out..


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## Joves (Jan 23, 2009)

Lokks like they are trying to do a knock off of the Singh Rays. Their 77mm is only $340 and well worth it if you use one enough. Singh-Ray Filters: Vari-ND Variable Neutral Density Filter I personally though prefer stacking filters over paying alot for a filter that does it for me.


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## Eldrich (Jan 23, 2009)

if you just stacked two polarizing filters, you'd get the same control.  you might have AF issues if you're not using circular polarizers, but as long as there are no strongly polarized light sources (i.e. reflections or sky at 90 degrees to the sun) they would behave just like a ND filter with variable control (spinning one polarizer with respect to the other) and since you already probably own one polarizer, a second one would be much cheaper than the filter mentioned in the OP.


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## Eldrich (Jan 23, 2009)

actually, now that i think about it, as long as you kept the circular polarizer as the inner filter, that is the filter just before the light entering the camera, you would not have any AF problems.  So you could get a cheap regular polarizer for the second one to go on top of the circular polarizer and have a very cheap variable ND filter, as long as you were okay with getting the effects of polarizing filters as well.


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## dEARlEADER (Jan 23, 2009)

Eldrich said:


> actually, now that i think about it, as long as you kept the circular polarizer as the inner filter, that is the filter just before the light entering the camera, you would not have any AF problems.  So you could get a cheap regular polarizer for the second one to go on top of the circular polarizer and have a very cheap variable ND filter, as long as you were okay with getting the effects of polarizing filters as well.



you will most likely introduce vignetting when stacking polarizers...

plus two polarizers only gets four stops.... whereas the cheap p.o.s. listed would give you up to 8 stops

or make the 8 EASY STOPS!!


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## Joves (Jan 23, 2009)

dEARlEADER said:


> you will most likely introduce vignetting when stacking polarizers...
> 
> plus two polarizers only gets four stops.... whereas the cheap p.o.s. listed would give you up to 8 stops
> 
> or make the 8 EASY STOPS!!


 Supposedly easy stops.


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## Eldrich (Jan 23, 2009)

dEARlEADER said:


> you will most likely introduce vignetting when stacking polarizers...
> 
> plus two polarizers only gets four stops.... whereas the cheap p.o.s. listed would give you up to 8 stops
> 
> or make the 8 EASY STOPS!!



yes, stacking filters may give you vignetting, but I mentioned it in response to someone saying they would stack ND filters.  

and actually, using two polarizing filters you could go from 1 stop, all the way to having absolutely no light making it to the camera. That is as long as the first polarizer was not a circular polarizer.  If it was a circular polarizer, then you could only take it down 2 stops I think, not 4 (?) how do you figure 4?  

The way I see it, with completely random polarization, the first filter can polarize all light say, vertically, which would effectively be 1 stop, then if the second polarizer were oriented 90 degrees to the first, no light would get through.  And as I said, if the first filter were a circular polarizer, then it would circularly polarize the light, and the most stop you could get from the second polarizer would be one more stop.


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## tirediron (Jan 23, 2009)

Eldrich said:


> ... using two polarizing filters you could go from 1 stop, all the way to having absolutely no light making it to the camera...


 
Interesting theory; not exactly sure I understand the physics you're talking about however.


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## Eldrich (Jan 23, 2009)

tirediron said:


> Interesting theory; not exactly sure I understand the physics you're talking about however.



Basically, if you imagine light traveling directly at you, the electric field of that light can vibrate in two different polarizations (for instance, horizontally or vertically), or it can be in a combination of the two different polarizations.  In general, random light will be a random combination of the two directions.  

A polarizing filter, if oriented in the horizontal direction, will block all light that oscillates in the horizontal direction.  If you were to rotate the polarizer by 90 degrees, it would block all vertically polarized light.  

So a polarizer will work as a 1 stop ND filter on completely randomly polarized light, it will block on average, half of the light.

Since the polarizer blocks all light that is horizontally polarized, all light that goes through  the polarizer is polarized vertically.  Then, the second polarizer can be oriented to block any amount of the light which you want it to.  If the second polarizer is aligned the same way as the first it would let all light through, because all of the light that made it through the first is already polarized vertically.  If you then rotated the second polarizer, you would see things get darker until the two polarizers were at 90 degrees to one another and then since the first polarizer only let vertical light through, the second polarizer would be oriented to only let horizontal light through, and so none would get through.

since light is a quantum system, there is a gradation between the two different polarizations, so you can get anything between half of the original light, to no light going through.

This website has a description of cross polarization:
Light and Polarization

but really, any optics book or physics book that discusses polarization will address the same thing.

If you want I can describe my comment about the circular polarizers having a limitation to 2 stops of ND, but only if you're interested, it would take a little more explanation.


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## tirediron (Jan 23, 2009)

Hmmmm...  have to give that a try.


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## Manlatiger (Jan 23, 2009)

well, true.
seems made in china products are still not having a good reputation.
however I asked the seller bout the glasses and they replied me, saying the filter glasses are from Polaroid and they are using imported glasses rather than made in china.
LOL, I think they know pretty well how bad China glasses are.
Looks like price dropped, I think I will give it a try.
Cheers


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## Eldrich (Jan 23, 2009)

Manlatiger, sorry the thread was somewhat hijacked into a discussion of polarization!

I only meant to convey that the effect of a variable ND filter could be achieved much cheaper than 300$ with two polarizing filters, but if the price dropped to 100$ and you are interested in having the ability to change a ND filter over a range, then perhaps it is worth it to buy a single filter that can do the job.

I cant say for certain, (in some circles 'polaroid' means a polarizing filter) but I suspect that this variable neutral density filter simply IS two polarizing filters mounted together, utilizing the effect I've been talking about.  If someone were to ask me how to design a variable ND filter, i would give them two polarizing filters.

Anyway, I would still be a little hesitant to spend 100$ for an effect I think you could get buying a second 20$ polarizing filter (assuming you already have one) but it's up to you.


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## Manlatiger (Jan 24, 2009)

Eldrich,
Thanks for your advice!
O, just wanna clarify, Polaroid glasses means the Glass Making Company Polaroid.


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## dEARlEADER (Jan 24, 2009)

Eldrich said:


> Manlatiger, sorry the thread was somewhat hijacked into a discussion of polarization!
> 
> I only meant to convey that the effect of a variable ND filter could be achieved much cheaper than 300$ with two polarizing filters, but if the price dropped to 100$ and you are interested in having the ability to change a ND filter over a range, then perhaps it is worth it to buy a single filter that can do the job.
> 
> ...




I am unsure of the science you speak of...

a basic polarizing filter reduces you exposure by approxmately two stops...


you can verify this simply by metering an image in manual overexposed by 2 stops...then add a polarizer to same exposure and find yourself equalized...... this is regardless of the position of the polarizer....

stacking another polarizer will double this effect... hence 4 stops ..

you are either much smarter than i...... or you are a dumb sh*t with a creative vocabulary....

i will submit to either result......  it is most likely that I am the dumb s*it so prove me wrong...


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## Eldrich (Jan 24, 2009)

dEARlEADER said:


> you can verify this simply by metering an image in manual overexposed by 2 stops...then add a polarizer to same exposure and find yourself equalized...... this is regardless of the position of the polarizer....
> 
> stacking another polarizer will double this effect... hence 4 stops ..
> 
> you are either much smarter than i...... or you are a dumb sh*t with a creative vocabulary.....


with my polarizing filter, testing my light meter, I get 1 and a third stop.
And to test my 'theory' that two crossed polarized filters will stop all light, I suggest you try it yourself, put two of them together, and rotate one with respect to the other, there will be an arrangement that doesn't let any light through.  

Stacking two polarizers does not just double the effect, you have to look up the physics of polarization.

I will say I am a PhD candidate in the field of atomic and optic physics, so I am pretty sure I know what I'm talking about when it comes to polarization physics...


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## Iron Flatline (Jan 24, 2009)

Joves said:


> Lokks like they are trying to do a knock off of the Singh Rays. Their 77mm is only $340 and well worth it if you use one enough. Singh-Ray Filters: Vari-ND Variable Neutral Density Filter I personally though prefer stacking filters over paying alot for a filter that does it for me.


Thanks for linking to this, looks like an interesting product.


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## dEARlEADER (Jan 24, 2009)

Eldrich said:


> I will say I am a PhD candidate in the field of atomic and optic physics, so I am pretty sure I know what I'm talking about when it comes to polarization physics...




my apologies..... i am the dumb s**t ..... i was looking at it from a simplistic approach...(and at 3:00am and intoxicated one as well)

i don't have two to try it out.... but sounds logical...

FWIW.... most polarizers i've searched out are rated two stops or just under... i've personally been looking for one with less density.. i could only find a "warming" polarizer rated at 1 1/3 stop..... what brand are you using?


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## AlexColeman (Jan 24, 2009)

The phrase that got me was "if you are tired of freezing the image, let it flows."


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## Eldrich (Jan 24, 2009)

It is a Zeikos CPL filter, pretty cheap actually. 

It could be that some of the polarizers have some additional loss for one reason or another.

You could certainly engineer two polarizers, and a dielectric coating (for a waveplate, and possibly antireflective), to get tunability between any range of ND. Which is probably what this company did.   If they did have some AR coatings to reduce glare from stacking filters, that would add a lot to the cost, but would make it a little better than two stacked polarizers.


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## Iron Flatline (Jan 24, 2009)

AlexColeman said:


> The phrase that got me was "if you are tired of freezing the image, let it flows."


I thought that was a good way of phrasing the potential of this filter.


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## Joves (Jan 24, 2009)

AlexColeman said:


> The phrase that got me was "if you are tired of freezing the image, let it flows."


 Yes but you can do that with a standard CP and low ISO with the f-stop closed down or, near down. Example this was shot at f/11 ISO 100 using a 1/4 second shutter. 





Closing the aperture would have gained more effect but I had enough wind that it would have screwed any detail of the trees.


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## Garbz (Jan 25, 2009)

The polarizing theory is right however perfect polarisers are very expensive. Even some of the filters in our optics lab produced irregularities accross their surface. Don't expect this to work with cheap filters.


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## fotojunky (Jan 21, 2010)

i tried stacking two polarizers filters it doesnt work well as you get very bad  vignetting i saw the fader nd on faderfilters.com it actually works great its amazing toy its worth every penny the effects are great its solidly made it cost me $129 on amazon it does drop 8 stops the only thing is the front lens cap size is not the same size so i had to hunt down another lens cap... saw on  faderfilters.com  website there releasing a hd version and was wondering if its worth it ?


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## guerillawerkz (Jul 1, 2010)

Pure said:


> Judging by the crappy English, and it's from china, it's probably low quality glass with a even crappier coating.


 
Crappy English means crappy quality? wtf is wrong with you?


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## Garbz (Jul 1, 2010)

guerillawerkz said:


> Crappy English means crappy quality? wtf is wrong with you?



I don't like feeding trolls but really you sign up to a forum simply to reply to a post that was made over a year ago, and you're asking what's wrong with him...

Nice.


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## djacobox372 (Jul 3, 2010)

If you're looking for a good filter look for the words "made in Germany."


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