strangways
Well-known member
Recently, I discovered a need for a polarizing filter on my DVX100A: filming people inside a car, through the front windshield, I needed a polarizer to cut out the reflections and clearly see inside.
I decided to search these wonderful forums to see what experience people had with polarizers, and I came across a lot of terrible misinformation. The general impression I got was that a number of people recommend circular polarizers over linear polarizers. Some even suggested that you NEED a circular. This is also what dealers are telling people - and why a friend of mine paid over $100 for a circular polarizer to use with his 100A.
It's time someone set the record straight.
"You need a circular polarizer with the DVX100(A), or it's at least better than a linear polarizer."
FICTION!
First of all, let me clarify a common misconception about polarizers: both are physically circular filters that screw into you lenses and then can be freely rotated to change the angle of polarization, and thus the effect of removing reflections or deepening the colour of a blue sky.
Both do the exact same thing to light entering them. To try and simplify, light "vibrates" in all directions when it leaves a light source, whether aritificial or natural. When it is reflected by most surfaces (other than metal) it beomes polarized, only vibrating in one direction. Reflected light from a horizontal surface is horizontally polarized, and vice-versa for vertical surfaces.
A polarizer is simply a screen, it only transmits light polarized in one direction, and rotating the polarizer alters that direction. So, if you have a reflection from a horizontal surface, and you rotate the polarizer until it ony allows vertically polarized light to pass, it effectively blocks the reflected light, and therefore the image of the reflection.
The difference between the two types of polarizers is in how light leaves the filter. A linear polarizer simply lets the light, now polarized in one direction only, continue on its way. A circular polarizer uses a "quarter-wave retarder" to essentially un-polarize the light, and get it vibrating in all directions again... still minus the reflection, of course.
The reason for this is that some Single-Lens Reflex still photography cameras use polarization in their autofocus and/or exposure systems. Light vibrating in a specific direction passes through the mirror reflecting light up the viewfinder, and hits a secondary mirror sending it down to a metering and/or autofocus sensor system. It's polarizing light.
The problem is that if your metering/AF system takes the vertically polarized light, and your polarizing filter is only letting through horizontally polarized light, the sensors receive no light at all, rendering them useless.
With a circular polarizer converting the light that is polarized in only one direction back into light polarized in all directions, the secondary mirror is able to do its job, and has light it can direct to the sensors.
I hope you followed along with all of that. But here's the catch:
FACT: that doesn't matter one bit to the DVX100(A)!
It does not have anything in its optical system that is affected by the polarization of light.
The autofocus and exposure systems are not separate sensors, they simply use the data from the CCDs. Even before that, the prism that separates the light into the primary colours and redirects them to the three CCDs isn't affected either, because the prism works with the wavelengths (or colours, if you prefer) of the light, and not the direction it's polarized in.
So, here's the definitive short list:
FACTS: Linear vs. Circular polarizers on the DVX100(A)
1) Autofocus works the same with either. So does manual.
2) Autoexposure works the same with either. So does manual.
3) The prism splitting light to the three CCDs works the same with either.
4) Anything else you can care to think of works the same with either.
The ONLY difference, and it's a BIG one:
5) Linear polarizers are cheaper than circular polarizers.
AND, believe it or not:
Linear polarizers are MORE effective than circular polarizers - they are better at blocking more of the light polarized in the direction you are trying to cut out. ...for reasons I'm too tired to get into now. Now, it's not a big difference, in fact you'd rarely notice it, but for all of the fiction that circular polarizers are better/more effective, the fact is that the opposite is true.
Now, believing as I do that practice will always win out over theory, I put it to the test. I visited a local photography store I have dealt with on a very regular basis, and was able to borrow two polarizers. A $153 B+W (Schneider) Circular Polarizer (top of the line Kasemann type) and a used Hoya Linear Polarizer worth... wait for it... $35.
Now, if I were putting the linear polarizer on a modern Single-Lens Reflex camera, it would stop the autofocus from functioning in most cases. In fact, it would also stop the metering system on my 1980's Olympus SLR cameras from working.
BUT, on the DVX100(A), there was absolutely NO difference. Everything on the camera functioned perfectly with the linear polarizer, just as it did with the circular.
I compared the quality of the image, looking at the effect of polarization, as well as the clarity and sharpness and lack of flare with the image in general, showed no discernible difference between the two.
So, why spend over FIVE TIMES MORE on the circular polarizer? Probably because the safe bet has seemed to be splurging on the circular just in case. Misinformation, uncertainty, and doubt.
Put it all to rest now. If you're looking to buy a polarizer, get a linear. Save your money. In fact, try and find a clean, scratch-free used one. Check a photography store. Not a giant electronics retail chain, but a local, independent store that carries used equipment.
I know this has been a long post, and I hope I haven't come across like a jerk. I'm not trying to shout out loud that I'm right; the simple fact is that I hoped to separate the fact from the fiction fully and clearly so all doubts could be laid to rest. I don't think my friend, or anyone on this board, ought to be paying more than they need to for an incredibly useful piece of kit. That's all there is to it.
Now, let's all get off our butts and go shoot something!
I decided to search these wonderful forums to see what experience people had with polarizers, and I came across a lot of terrible misinformation. The general impression I got was that a number of people recommend circular polarizers over linear polarizers. Some even suggested that you NEED a circular. This is also what dealers are telling people - and why a friend of mine paid over $100 for a circular polarizer to use with his 100A.
It's time someone set the record straight.
"You need a circular polarizer with the DVX100(A), or it's at least better than a linear polarizer."
FICTION!
First of all, let me clarify a common misconception about polarizers: both are physically circular filters that screw into you lenses and then can be freely rotated to change the angle of polarization, and thus the effect of removing reflections or deepening the colour of a blue sky.
Both do the exact same thing to light entering them. To try and simplify, light "vibrates" in all directions when it leaves a light source, whether aritificial or natural. When it is reflected by most surfaces (other than metal) it beomes polarized, only vibrating in one direction. Reflected light from a horizontal surface is horizontally polarized, and vice-versa for vertical surfaces.
A polarizer is simply a screen, it only transmits light polarized in one direction, and rotating the polarizer alters that direction. So, if you have a reflection from a horizontal surface, and you rotate the polarizer until it ony allows vertically polarized light to pass, it effectively blocks the reflected light, and therefore the image of the reflection.
The difference between the two types of polarizers is in how light leaves the filter. A linear polarizer simply lets the light, now polarized in one direction only, continue on its way. A circular polarizer uses a "quarter-wave retarder" to essentially un-polarize the light, and get it vibrating in all directions again... still minus the reflection, of course.
The reason for this is that some Single-Lens Reflex still photography cameras use polarization in their autofocus and/or exposure systems. Light vibrating in a specific direction passes through the mirror reflecting light up the viewfinder, and hits a secondary mirror sending it down to a metering and/or autofocus sensor system. It's polarizing light.
The problem is that if your metering/AF system takes the vertically polarized light, and your polarizing filter is only letting through horizontally polarized light, the sensors receive no light at all, rendering them useless.
With a circular polarizer converting the light that is polarized in only one direction back into light polarized in all directions, the secondary mirror is able to do its job, and has light it can direct to the sensors.
I hope you followed along with all of that. But here's the catch:
FACT: that doesn't matter one bit to the DVX100(A)!
It does not have anything in its optical system that is affected by the polarization of light.
The autofocus and exposure systems are not separate sensors, they simply use the data from the CCDs. Even before that, the prism that separates the light into the primary colours and redirects them to the three CCDs isn't affected either, because the prism works with the wavelengths (or colours, if you prefer) of the light, and not the direction it's polarized in.
So, here's the definitive short list:
FACTS: Linear vs. Circular polarizers on the DVX100(A)
1) Autofocus works the same with either. So does manual.
2) Autoexposure works the same with either. So does manual.
3) The prism splitting light to the three CCDs works the same with either.
4) Anything else you can care to think of works the same with either.
The ONLY difference, and it's a BIG one:
5) Linear polarizers are cheaper than circular polarizers.
AND, believe it or not:
Linear polarizers are MORE effective than circular polarizers - they are better at blocking more of the light polarized in the direction you are trying to cut out. ...for reasons I'm too tired to get into now. Now, it's not a big difference, in fact you'd rarely notice it, but for all of the fiction that circular polarizers are better/more effective, the fact is that the opposite is true.
Now, believing as I do that practice will always win out over theory, I put it to the test. I visited a local photography store I have dealt with on a very regular basis, and was able to borrow two polarizers. A $153 B+W (Schneider) Circular Polarizer (top of the line Kasemann type) and a used Hoya Linear Polarizer worth... wait for it... $35.
Now, if I were putting the linear polarizer on a modern Single-Lens Reflex camera, it would stop the autofocus from functioning in most cases. In fact, it would also stop the metering system on my 1980's Olympus SLR cameras from working.
BUT, on the DVX100(A), there was absolutely NO difference. Everything on the camera functioned perfectly with the linear polarizer, just as it did with the circular.
I compared the quality of the image, looking at the effect of polarization, as well as the clarity and sharpness and lack of flare with the image in general, showed no discernible difference between the two.
So, why spend over FIVE TIMES MORE on the circular polarizer? Probably because the safe bet has seemed to be splurging on the circular just in case. Misinformation, uncertainty, and doubt.
Put it all to rest now. If you're looking to buy a polarizer, get a linear. Save your money. In fact, try and find a clean, scratch-free used one. Check a photography store. Not a giant electronics retail chain, but a local, independent store that carries used equipment.
I know this has been a long post, and I hope I haven't come across like a jerk. I'm not trying to shout out loud that I'm right; the simple fact is that I hoped to separate the fact from the fiction fully and clearly so all doubts could be laid to rest. I don't think my friend, or anyone on this board, ought to be paying more than they need to for an incredibly useful piece of kit. That's all there is to it.
Now, let's all get off our butts and go shoot something!
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