POLARIZER "effectiveness" ???

I think a loss of between 0.5% and 0.1% is more likely.

It is difficult to get good specs on a high quality quarter wave film. The link below points to an internal transmittance of 99% for a good quality film. So the loss of 1%. But typically numbers like that are worst case. The manufacturers want to be on solid ground when rejecting returns.

AQWP3 – Bolder Vision Optik

When I have measured similar thing in the lab, with the film in between glass plates, it has been hard to separate out the loss from the front and back surface Fresnel reflections. My estimates of internal loss have been around 0.5% to 0.2%, but I did not make a serious study of it.

The quarter wave film used in things like computer displays are a good step down in quality. Haze on those runs about 0.3%.

Most of the time when I am using quarter wave plates, it is for laser use, and the quarter wave plates are made from crystalline quartz. Internal transmittance losses on those are vanishingly small. Like 0.0001%. And there is no haze at all.

Every time I have tried to reduce cost by using a film, even a high quality film, performance takes a big hit. Haze is always a problem. And it is easily seen. Just look for light scattered out of the main beam on a piece of paper held next to the beam.

The debate on if something like 0.001% is zero or not I find amusing. Depending on what projects I have worked on, sometimes 0.001% is down in the noise and zero for any practical reasons. But other times, 0.001% has been the signal we are after. So I have been on both sides of that debate at times.

Thanks for your interesting reply.

OpticsEngineer said:

I think a loss of between 0.5% and 0.1% is more likely.

It is difficult to get good specs on a high quality quarter wave film. The link below points to an internal transmittance of 99% for a good quality film. So the loss of 1%. But typically numbers like that are worst case. The manufacturers want to be on solid ground when rejecting returns.

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I like that answer. For what it's worth, I wrote "probably under 1%".

OpticsEngineer said:

AQWP3 – Bolder Vision Optik

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Weird that they use a fused polymer stack for some strange reason.

OpticsEngineer said:

When I have measured similar thing in the lab, with the film in between glass plates, it has been hard to separate out the loss from the front and back surface Fresnel reflections. My estimates of internal loss have been around 0.5% to 0.2%, but I did not make a serious study of it.

The quarter wave film used in things like computer displays are a good step down in quality. Haze on those runs about 0.3%. Most of the time when I am using quarter wave plates, it is for laser use, and the quarter wave plates are made from crystalline quartz. Internal transmittance losses on those are vanishingly small. Like 0.0001%. And there is no haze at all.

Click to expand...

OpticsEngineer said:

Every time I have tried to reduce cost by using a film, even a high quality film, performance takes a big hit. Haze is always a problem. And it is easily seen. Just look for light scattered out of the main beam on a piece of paper held next to the beam.

The debate on if something like 0.001% is zero or not I find amusing.

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Of course, 0.001% included only internal surface reflections, for one surface only, and admittedly for optimistically matched refractive indices. But in any case, it must be quite small.

OpticsEngineer said:

Depending on what projects I have worked on, sometimes 0.001% is down in the noise and zero for any practical reasons. But other times, 0.001% has been the signal we are after. So I have been on both sides of that debate at times.

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In this case, even 1% pales in comparison to ~65% attenuation by the polarizer.

Again, most of the imperfections that you measure are significant for your use, but probably insignificant for photography.

PhotoTeach2 said:

Question #1

Prior Polarizers had about a 2-stop loss.

Newer ones have much less loss, (some only about .5-stop).

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That's physically impossible. An ideal hypothetical polarizer will cut out exactly a half of the randomly polarized incoming light. 1 stop of light loss is the theoretical minimum. In practice, the loss is always a bit more than 1 stop because some of the light that should have passed is lost.

PhotoTeach2 said:

From prior experience, do you know if the newer (less-loss) are LESS EFFECTIVE ???

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I am pretty sure they don’t exist. If they lose only 0.5 stop, they should not be called polarizing filters.

PhotoTeach2 said:

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Question #2

Also, are circular-polarizers any LESS-EFFECTIVE than "linear" ???

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No.

PhotoTeach2 said:

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Question/comment #3

Since MirrorLess cameras can now use "linear", (w/out the mirror/exposure problems from SLR/dSLR), do you wish there were more (less-expensive) linear-PL available ???

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No. Makes no difference to the image.

PhotoTeach2 said:

Seems like (only) the "C"PL's have the best multi-coating .... ???

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I don't see why new linear polarizers would not have the same coating as new CPLs. Those linear polarizers that were made before the SLRs came about and triggered the switch from linear to CPL are just too old to have the multi-coating we have nowadays.

PhotoTeach2 said:

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So basically, if I am going to carry/use a "polarizer", I want the MOST EFFECTIVE, (and cheapest if that can be a "linear") !!!

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For everyday photography, their "effectiveness" in blocking polarized light is the same. Their price point will indicate how much they degrade image quality, same as with UV filters.

PhotoTeach2 said:

But I don't mind the sacrifice of 2-stop loss if necessary to be "most-effective".

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Dem Bell said:

PhotoTeach2 said:

Question #1

Prior Polarizers had about a 2-stop loss.

Newer ones have much less loss, (some only about .5-stop).

Click to expand...

That's physically impossible. An ideal hypothetical polarizer will cut out exactly a half of the randomly polarized incoming light. 1 stop of light loss is the theoretical minimum. In practice, the loss is always a bit more than 1 stop because some of the light that should have passed is lost.

Click to expand...

Polarizer - Wikipedia Malus' Law



Since the average value of cos^2⁡ is 1/2, the transmission coefficient becomes

J A C S said:

Dem Bell said:

PhotoTeach2 said:

Question #1

Prior Polarizers had about a 2-stop loss.

Newer ones have much less loss, (some only about .5-stop).

Click to expand...

That's physically impossible. An ideal hypothetical polarizer will cut out exactly a half of the randomly polarized incoming light. 1 stop of light loss is the theoretical minimum. In practice, the loss is always a bit more than 1 stop because some of the light that should have passed is lost.

Click to expand...

Polarizer - Wikipedia Malus' Law

Since the average value of cos^2⁡ is 1/2, the transmission coefficient becomes

Click to expand...

Which confirms what I said. The reduction by a factor of two is "one stop", not "0.5 stop".

J A C S said:

Dem Bell said:

PhotoTeach2 said:

Question #1

Prior Polarizers had about a 2-stop loss.

Newer ones have much less loss, (some only about .5-stop).

Click to expand...

That's physically impossible. An ideal hypothetical polarizer will cut out exactly a half of the randomly polarized incoming light. 1 stop of light loss is the theoretical minimum. In practice, the loss is always a bit more than 1 stop because some of the light that should have passed is lost.

Click to expand...

Polarizer - Wikipedia Malus' Law

Since the average value of cos^2⁡ is 1/2, the transmission coefficient becomes

Click to expand...

A good article.

However, it states: "However, cameras with through-the-lens metering (TTL) and autofocusing systems – that is, all modern SLR and DSLR – rely on optical elements that pass linearly polarized light." When discussing polarizer types for photography, it is rarely mentioned that many camera sensors have birefringent low-pass filters, which will also be subject to interference by a linear polarizer.

Dem Bell said:

J A C S said:

Dem Bell said:

PhotoTeach2 said:

Question #1

Prior Polarizers had about a 2-stop loss.

Newer ones have much less loss, (some only about .5-stop).

Click to expand...

That's physically impossible. An ideal hypothetical polarizer will cut out exactly a half of the randomly polarized incoming light. 1 stop of light loss is the theoretical minimum. In practice, the loss is always a bit more than 1 stop because some of the light that should have passed is lost.

Click to expand...

Polarizer - Wikipedia Malus' Law

Since the average value of cos^2⁡ is 1/2, the transmission coefficient becomes

Click to expand...

Which confirms what I said. The reduction by a factor of two is "one stop", not "0.5 stop".

Click to expand...

Yes, I just wanted to add to it.

Dem Bell said:

J A C S said:

Dem Bell said:

PhotoTeach2 said:

Question #1

Prior Polarizers had about a 2-stop loss.

Newer ones have much less loss, (some only about .5-stop).

Click to expand...

That's physically impossible. An ideal hypothetical polarizer will cut out exactly a half of the randomly polarized incoming light. 1 stop of light loss is the theoretical minimum. In practice, the loss is always a bit more than 1 stop because some of the light that should have passed is lost.

Click to expand...

Polarizer - Wikipedia Malus' Law

Since the average value of cos^2⁡ is 1/2, the transmission coefficient becomes

Click to expand...

Which confirms what I said. The reduction by a factor of two is "one stop", not "0.5 stop".

Click to expand...

Doesn't this really only apply to a perfect/ideal polarizer?

An imperfect one that leaks some light when completely cross-polarized would achieve lower total losses - but at the cost of doing its primary job poorly. Not worth the tradeoff for the vast majority of use cases, so anyone advertising less than a stop of loss is basically saying "We're selling cheap junk and declaring our poor performance at doing our primary task to be a feature".

--
Context is key. If I have quoted someone else's post when replying, please do not reply to something I say without reading text that I have quoted, and understanding the reason the quote function exists.

Entropy512 said:

Dem Bell said:

J A C S said:

Dem Bell said:

PhotoTeach2 said:

Question #1

Prior Polarizers had about a 2-stop loss.

Newer ones have much less loss, (some only about .5-stop).

Click to expand...

That's physically impossible. An ideal hypothetical polarizer will cut out exactly a half of the randomly polarized incoming light. 1 stop of light loss is the theoretical minimum. In practice, the loss is always a bit more than 1 stop because some of the light that should have passed is lost.

Click to expand...

Polarizer - Wikipedia Malus' Law

Since the average value of cos^2⁡ is 1/2, the transmission coefficient becomes

Click to expand...

Which confirms what I said. The reduction by a factor of two is "one stop", not "0.5 stop".

Click to expand...

Doesn't this really only apply to a perfect/ideal polarizer?

Click to expand...

Sure.

Entropy512 said:

An imperfect one that leaks some light when completely cross-polarized would achieve lower total losses - but at the cost of doing its primary job poorly.

Click to expand...

The amount of light a real polarizer "leaks" in the direction it is supposed to block everything is negligible. The worst case scenario in the visible spectrum is for the blue light and even then it is only a couple of percent.

The real polarizer will block much more light in the direction it is supposed to pass everything, say about 50%, and that's how we might end up with about 2 stop loss for non-polarized light.

Entropy512 said:

Not worth the tradeoff for the vast majority of use cases, so anyone advertising less than a stop of loss is basically saying "We're selling cheap junk and declaring our poor performance at doing our primary task to be a feature".

Click to expand...

I couldn't find any manufacturer advertising their polarizers having less than a stop light loss. Any links, anyone?

Dem Bell said:

I couldn't find any manufacturer advertising their polarizers having less than a stop light loss. Any links, anyone?

Click to expand...

OP appears to have found one, unfortunately didn't provide a link to it. Either marketing BS, or very poor quality and does not do its job very well.

Entropy512 said:

Dem Bell said:

J A C S said:

Dem Bell said:

PhotoTeach2 said:

Question #1

Prior Polarizers had about a 2-stop loss.

Newer ones have much less loss, (some only about .5-stop).

Click to expand...

That's physically impossible. An ideal hypothetical polarizer will cut out exactly a half of the randomly polarized incoming light. 1 stop of light loss is the theoretical minimum. In practice, the loss is always a bit more than 1 stop because some of the light that should have passed is lost.

Click to expand...

Polarizer - Wikipedia Malus' Law

Since the average value of cos^2⁡ is 1/2, the transmission coefficient becomes

Click to expand...

Which confirms what I said. The reduction by a factor of two is "one stop", not "0.5 stop".

Click to expand...

Doesn't this really only apply to a perfect/ideal polarizer?

An imperfect one that leaks some light when completely cross-polarized would achieve lower total losses - but at the cost of doing its primary job poorly.

Click to expand...

That is exactly my point and question.

Entropy512 said:

Not worth the tradeoff for the vast majority of use cases, so anyone advertising less than a stop of loss is basically saying "We're selling cheap junk and declaring our poor performance at doing our primary task to be a feature".

Click to expand...

Yes ... I want the most "effective" polarizer.

Entropy512 said:

Dem Bell said:

I couldn't find any manufacturer advertising their polarizers having less than a stop light loss. Any links, anyone?

Click to expand...

OP appears to have found one, unfortunately didn't provide a link to it. Either marketing BS, or very poor quality and does not do its job very well.

Click to expand...

OK ... I submit I was WRONG (or exaggerating) by specifically stating .5-stop.

It does appear that the lowest is indeed only "1"-stop.

BUT ... my question is still if they are as "effective" as the more typical -2-stop CPL's.

My point is that I want the most "effective", and if that requires a -2-stop ... OK

But obviously, the -1-stop would be preferable if there is no compromise in "effectiveness".

And by the same token, a cheaper linear would also be preferable (on ML camera) if as effective ... and my recollection back from film days is that linear-p seemed to be more effective than today's CPL.

PhotoTeach2 said:

Entropy512 said:

Dem Bell said:

I couldn't find any manufacturer advertising their polarizers having less than a stop light loss. Any links, anyone?

Click to expand...

OP appears to have found one, unfortunately didn't provide a link to it. Either marketing BS, or very poor quality and does not do its job very well.

Click to expand...

OK ... I submit I was WRONG (or exaggerating) by specifically stating .5-stop.

It does appear that the lowest is indeed only "1"-stop.

BUT ... my question is still if they are as "effective" as the more typical -2-stop CPL's.

Click to expand...

How do you quantify "effectiveness"?

EDIT: just reread this thread, you said:

PhotoTeach2 said:

Well, by "effective" I mean how "blue" it intensities the sky, or reflections decrease.

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To which ThrillaMozilla replied: "There is absolutely no difference in that respect that you will ever be able to see or measure." My thoughts exactly.

Also, why do we assume that 2 stops are typical? I had about 10 polarizers at some point and measured how much non-polarized light they blocked. All came out between 1.4 and 1.8 stops. Now the sales pitch goes like this: "it used to be about 2 stops, but now it is between 1 and 1.5 stop". In reality, it used to be 1.6 stop, but now it is 1.4 stop. Nothing really changed.

PhotoTeach2 said:

My point is that I want the most "effective", and if that requires a -2-stop ... OK

But obviously, the -1-stop would be preferable if there is no compromise in "effectiveness".

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I very much doubt that (1) it is ever going to be 1-stop and (2) you would be able to tell which one of two polarizers is more "effective".

PhotoTeach2 said:

And by the same token, a cheaper linear would also be preferable (on ML camera) if as effective ... and my recollection back from film days is that linear-p seemed to be more effective than today's CPL.

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That is what you might think, but they were not. They were slightly worse than today's CPL (do you really think that technology is getting worse?) but you would need to run dedicated tests to figure that out. No difference will be evident in photographic images ala darkening the sky.