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Zhao, D., & Guo, H. (2018). A Trajectory Planning Method for Polishing Optical Elements Based on a Non-Uniform Rational B-Spline Curve. Applied Sciences, 8(8), 1355. https://doi.org/10.3390/app8081355

While we’re on the subject of reducing reflections with polarizers, I’d like to say that it has always struck me as odd that we use uncoated filters in cinematography.

You may well want to remove enough reflection that you can see through the window or windshield, but not so much that the glass disappears . . .

Zhao, D.; Guo, H. A Trajectory Planning Method for Polishing Optical Elements Based on a Non-Uniform Rational B-Spline Curve. Appl. Sci. 2018, 8, 1355. https://doi.org/10.3390/app8081355

You can get as much as 4% reflection per surface on flat glass. That’s 8% per filter (2 sides). If you have just two filters in your matte box, 16% of the light entering your system is going somewhere unintended . . . reducing contrast and color saturation. It’s “stray light” or flare.

I don’t personally recall an ultra thin Kaesemann polarizer from my time at Schneider. I don’t doubt that it existed and may still exist, it’s just that the B+W product range is HUGE.

A number of years ago I bought a Canon 100/400 still zoom. It wasn’t very sharp at 400 mm. I realized it was because I was using the basic Canon Pola filter on it. I found that B+W offered an Ultra THIN Kaesmann Pola filter, designed especially for long lenses. Fairly expensive … if I recall $275 for a 77 mm filter … 11 years ago … but it made all the difference in the world! There must not be a market for it because I recently tried to find it in another size and could not locate one, Dwight.

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Linear vs circularpolarizer reddit

There is a much more scientific explanation for all this, so I do apologize for the over simplification of a science. Dwight Lindsey at Lindsey Optics can probably give you a much more thorough answer.

While we’re on the subject of reducing reflections with polarizers, I’d like to say that it has always struck me as odd that we use uncoated filters in cinematography.

Now some details: A circular polarizer is a linear polarizer with an added component, a clear layer called a quarter-wave retarder. The retarder layer has to be on the side of the filter that faces the camera lens in order to work properly. The linear polarizer component of both filters is generally identical (for a given manufacturer) and as such performs the same functions within the image.

Linear polarizationexample

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On the square, rectangular and cine round filter front: Many years ago, we at Schneider introduced the True-Pol polarizers in linear and circular. They were, in my opinion, better than the currently available product for cine matte boxes. Tiffen then matched us with the Ultra-Pol, which is, in my opinion, equivalent.

With a circular pol, the quarter wave plate on the rear of the polarizer spins the light so that the partial mirror in the video tap doesn’t cross polarize and block the light. So if there are mirrors in your optical system, the circular pol solves any problems or potential problems.

Linear polarization

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Polarizers have tiny parallel lines which pass light polarized in one direction and clip light with other polarizations. When the lines are closer together, the polarization is better . . . and the transmission is less. So as manufacturers, we need to choose between better polarization and better transmission.

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Hey Y'all I'm sure this has been covered, but what is the advantage of a circular polarizer vs linear? When would you use one vs the other? If you are building your own kit, which is the most useful if you can only buy one. Asking for a friend ;) John Tarver, csc DP in even snowier Toronto

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John: short answer—get a circular polarizer. It works in the same way as the linear, but does not have problems with certain internal camera and other optical systems. You can use it with most anything. The only drawbacks are that you need to know to mount it facing a certain way relative to the lens, and it costs a bit more than a linear.

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The polarizer, either circular or linear, allows management of polarized light in the scene. Effects include providing deeper blue sky and more dramatically white clouds; reducing or eliminating reflections from the surfaces of windows or water; increasing color saturation of certain objects in bright sunlight; and so on. The difference is that the circular polarizer, as mentioned earlier, actually serves to, in effect, depolarize the light after the polarizer layer has done its job for image management, and before the light enters the camera. This was initially offered years ago as a solution to the then-new auto-focus/auto-exposure cameras that bounced light off a partially silvered mirror, or beamsplitter, within the camera that directed some of the light to the sensor that determined exposure/focus. Since this reflected light is polarized, it will suffer adversely for having polarized light entering the camera system. Given the low chance that the light entering the system through the polarizer will be in the same polarization angle as the beamsplitter, since you have to rotate the polarizer according to what is required for each scene, the auto-focus/-exposure would likely not function as designed. The quarter-wave retarder effectively temporally corkscrews the linearly polarized light to eliminate the problem. Just be sure the circular polarizer is mounted with the retarder facing the lens. For round filters, this should be done by the manufacturer when the filter is placed in the ring (which only attaches one way). For square filters, the manufacturer will mark “This Side Out” on the glass so you know. If there is no marking for some reason, look through the filter and put the side facing the lens that is the side that through which you can see the polarization effects. The other side you won’t.

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Abstract: Optical polishing can accurately correct the surface error through controlling the dwell time of the polishing tool on the element surface. Thus, the precision of the trajectory and the dwell time (the runtime of the trajectory) are important factors affecting the polishing quality. This study introduces a systematic interpolation method for optical polishing using a non-uniform rational B-spline (NURBS). A numerical method for solving all the control points of NURBS was proposed with the help of a successive over relaxation (SOR) iterative theory, to overcome the problem of large computation. Then, an optimisation algorithm was applied to smooth the NURBS by taking the shear jerk as the evaluation index. Finally, a trajectory interpolation scheme was investigated for guaranteeing the precision of the trajectory runtime. The experiments on a prototype showed that, compared to the linear interpolation method, there was an order of magnitude improvement in interpolation, and runtime, errors. Correspondingly, the convergence rate of the surface error of elements improved from 37.59% to 44.44%. Keywords: hybrid robot; curve fitting; fair optimisation; trajectory interpolation

Linearpolarizervs circularpolarizer photography

As an aside, I’m always amused that physicists describe light as a wave, when it’s convenient (colors and polarization). They describe it as a particle, when it’s convenient (photons, photo-electric solar panels). When they speak quantum physics, things get really strange.

One problem that the circular polarizer addresses is other reflective surfaces in your system. The classic one in film was the video tap. Using a linear polarizer on a film camera with a video tap, could and often would cause the video feed to go dark.

There are a lot of articles that cover this actually. I spent a lot of time researching this as Abel Cine's Rental Manager back in the day and Mitch Gross and I used to have hour long conversations about it. So I feel your pain.

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Wow Don’t know where I’ve been but I never knew there were better polarizers - just thought they were all the same . What about Kaeseman polarizers, what the heck are those anyway? Good or Bad?

I have it summed up in my head pretty simply. Polarizers compensate for reflections of light. A linear polarizer will block deflected light from a specific angle. So as you rotate that filter, you can change the source of reflections directly. Circular Polarizers are a more complex system that block out reflections from multiple angles at once. So typically you will get cleaner images through office windows and on water and such but you have to play around a bit more to find the exact position of the filter for the best result.

Linear vs circular polarizationcar

For as long as anyone can recall, small round screw-in filters for photography have had good multi-layer anti-reflection coating (MC coating).

If it’s still of interest, I suggest you call Kevin in the New York Schneider Optics office, he knows everything about the Schneider B+W and Kaesemann filter product range.

Zhao, Dong, and Hao Guo. 2018. "A Trajectory Planning Method for Polishing Optical Elements Based on a Non-Uniform Rational B-Spline Curve" Applied Sciences 8, no. 8: 1355. https://doi.org/10.3390/app8081355

Our Zygo Phase Shift laser interferometer is available to members of this list. Feel free to bring a filter or filters to our shop North of Los Angeles, or send them to us.

Dwight - This has bothered me for some time. I have made this inquiry of both Tiffen and Schneider and the response was the same both times - "we certainly could coat filters, but there has never been a demand to do so. If there was high enough demand, we'd do it."

I tried a number of times to get my team at Schneider Optics to do AR coating and I always failed to get it done. I got the same answer as you report.

I don’t imagine that the thickness or thinness of the filter was the primary problem or solution. For long lenses filters really need to be flat within fractions of a wavelength of light. You can test that either with a laser interferometer in a lab . . . or as you did in a more practical way, by putting the filter on a long lens and observing the difference between sharpness with no filter and sharpness with the filter in place.

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s-polarizationvsppolarization

In fact a Circular Polarizer contains a Linear Polarizer component. It has a second layer inside the filter called a Quarter Wave Plate, which “spins” the light after it goes through the linear layer.

We’re also putting a serial number on every filter. So we’ll know who we sold it to and when we sold it. I suppose this might also be useful to rental houses.

Now that I have my own company, with a much smaller team, I feel able to just decide to do it, without any need to “encourage” the team.

A very flat filter with good surface quality (scratch/dig) and an AR coating, won’t have a negative effect on image quality with long lenses, even if its not “ultra thin”. BTW, normal small round screw-in filters are often 2mm thick. Round drop-in filters in 138mm and 4.5” by the major manufacturers, and us newbies, are usually 3.43mm thick.

aberration, n. meanings, etymology, pronunciation and more in the Oxford English Dictionary.

The linear polarizer element in the filter needs to be pointed at the world, with the quarter wave plate on the rear side, the camera lens side. A circular polarizer doesn’t work if you get it in backwards. With a screw-in filter that’s no issue. With drop-in and rectangular filters for matte boxes, the filters are labeled with “this side out”.

Zhao, D.; Guo, H. A Trajectory Planning Method for Polishing Optical Elements Based on a Non-Uniform Rational B-Spline Curve. Appl. Sci. 2018, 8, 1355. https://doi.org/10.3390/app8081355

The only difference is that the circular polarizer includes a quarter wave retarder after the polarizer. If you only buy one, the circular is pretty much all purpose. The polarizer filter is used to block polarized light (Reflections are polarized, while ambient light is scattered) By rotating the filter so as to be cross axis to the polarized light (reflections) it will block them. As the rest of the light passes through the filter it becomes polarized. This now polarized light can sometimes be problematic for some systems particularly those using semi mirrored surfaces to read exposure. In this case you need a circular polarizer, that in effect will un-polarize the light passing through the filter. Having the quarter wave retarder and not needing it will cause no harm.

For as long as anyone can recall, small round screw-in filters for photography have had good multi-layer anti-reflection coating (MC coating).

Kaesemann is a brand name, owned by Schneider. There was a Kaesemann company, which was purchased by Schneider quite some time ago. Kaesmann was famous for high quality polarizers and Schneider has maintained the high quality level for the brand. When I was with Schneider, Kaesamann was only available in small round screw-in filters. I believe that’s still true

Zhao D, Guo H. A Trajectory Planning Method for Polishing Optical Elements Based on a Non-Uniform Rational B-Spline Curve. Applied Sciences. 2018; 8(8):1355. https://doi.org/10.3390/app8081355

The short answer is in fact that both Linear and Circular Polarizers do the same thing. The actual polarization effects such as reducing reflections on glass surfaces, increasing color saturation in foliage, darkening a blue sky . . . are the same with Linear and Circular.

If you have no mirrors in your system, such as video tap a DSLR mirror or a beam splitter . . . then the Linear-Pol will not cause you any trouble and you can’t put it in the matte box backwards, which might save you some time and trouble.

Circular vs linearpolarizer for mirrorless camera

Top 5 Reasons To Own a Circular Polarizer Controls reflections on glass, water, leaves, and sky. Improves contrast Increases color saturation Removes ...

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Zhao D, Guo H. A Trajectory Planning Method for Polishing Optical Elements Based on a Non-Uniform Rational B-Spline Curve. Applied Sciences. 2018; 8(8):1355. https://doi.org/10.3390/app8081355

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