polarizer – How do I remove specular reflection from metal and plastic glasses product photos?

I’m trying to take product photos of some eye glasses.

The glasses are metal and plastic. For these photos, the LENSES are REMOVED so they do not constitute a problem.

I am trying to photograph the frames without ANY specular reflection. I’ve had a lot of success taming the specular reflection by doing the following.

1 – Linearly polarize the light sources and the lens.
2 – Move lights in angles where the specular reflection is minimized.
3 – Remove all other unpolarized light sources (dark room)

Although I’ve been able to greatly reduce the specular reflection, there is still the reflections of the light bulbs themselves as tiny spots or smudges on the plastic and metal glass surfaces.

Is there any method that would allow me to get rid of any and all specular reflection in this scenario?

Thank you

polarizer – Why do polarising filters only work in one direction?

The digital camera sports automation that adjusts exposure and focus. These mechanisms are likely dependent on semi-silvered mirrors. These work like mirrored sunglasses; they pass some light and reflect the remainder. When you mount a polarizing filter, it can be an impairment diminishing the effectiveness of this wonderful automation. Because mounting a polarizing filter is often desirable, we need one that will not do mischief.

The polarizing filter we use is actually two filters sandwiched together. The front facing filter is an ordinary polarizing linear screen. This one does the job. It mitigates reflections, cuts haze, and increases saturation. Because it darkens blue sky, white clouds are caused to stand out in bold relief. So it’s the upfront filter that does the deed.

Behind the polarizing screen is mounted a second filter called a retarder. This filter effectively de-polarizes the light. This sandwich filter is now called a circular polarizer. That’s OK because the upfront polarizing screen’s actions are not impaired and neither is the camera’s automation. If you turn this “circular” polarizer around, you effectively mitigate its ability to polarize light.

By the way, early scientists working with materials that polarized light falsely assumed that light had a + and – component, something like a magnet has a North and South Pole. They assumed the filter somehow split light into positive and negative (polarized) light beams. This was proven false but the name polarization stuck.

Most would agree, the polarizing filter is a must have filter.

Polarizer: Can looking at a computer screen show the difference between linear and circular polarizing filters?

The screen has cut out the linear polarizers, so all white light will be blocked. The first would let in a direction light, but the second would only pass the light that was blocked. Unless the layers of glass sandwiched between them are induced by electrons to activate the polarization of the passing light, so that the second one can pass. You can then rotate R G and B independently and to varying degrees, giving you shades of gray and color. This is obviously non-linear as it is about converting current based polarization.

So you put a third polarizer up front. If it's linear, you can align it with the second polarizer and it passes the same light as the second, so it's still white (with a slight ND effect). Then it aligns it with the first pol filter and then blocks all the light that was rotated to pass the second one and it's black.

Then you take a circular polarizer in this "rectified linear" light. What effect you get is less predictable. The cir-pol has a quarter wave on one side and a linear polarizer on the other side. if I hold it with the quarter wave towards the screen, it converts linear polarized light into circular polarized light, with 2 directions with a phase change between the two. blue is passed more than one side, and green and red on the other side. See graphs C1 and C2. Blue vs. Yellow / Orange are opposites. Orange is yellow with more red. yellow is red + green in the additive world. Therefore, it is basically opposite to blue, but with more red light passing by, as polarizer spectra often show. So we have some opposite effects here.

If you keep the quarter wave away from the screen, it turns black and white, because the way the linear polarizer in the cir-pol filter comes first and the passing light hits the quarter wave and polarizes in place .

Here I have both types of pol filters and I just tried them both. It is true that linear makes black / white and circular makes blue / yellow when you look at the part in front of the camera towards the screen. If you face that part towards yourself, it acts as the linear polarizer

Nikon: bullet points after using circular polarizer and Cokin system

I have a Nikon D750 camera with a lens that has a focal length of 24-70 mm and a lens diameter of 72 mm. I bought a circular polarizer and filters from the Cokin P system with a wide angle filter holder. But there are some bullets at 24 mm. What system should I buy to remove bullets? Is the P system small and should I use XL? Cokin system with circular polarizer.

Cokin system without polarizer.

The first photo is with a Cokin filter and circular polarizer.
and the second photo is a Cokin filter without circular polarizer

Polarizer: Is the Cokin 173 filter just a back CPL?

Is the Cokin 173 filter just a back CPL?

No. The effect is similar to mounting your polarizer back, but much more pronounced in the Varicolor filter.

This is what my Hoya HD CPL looks like at polarization angles of 0 ° and 90 °, when it is oriented for proper mounting (male threads towards the camera):

  • Note that this is NOT a variable ND filter. In the image on the right, the filter darkens the light because the light source is polarized (it comes from an LCD screen, which uses polarization to control the light output).

Circular polarizer, 0 ° rotation, mounted correctlyCircular polarizer, 90 ° rotation, mounted correctly
Hoya circular polarizer, normal orientation, at 0 ° (left) and 90 ° polarization (right)

When you turn the polarizer backwards, this is how it looks, again at polarization angles of 0 ° and 90 °.

  • Note that the automatic white balance of my iPhone tried to adjust to the color change in both images. The left bluish mold of the polarizer is actually more pronounced than shown. You can see the yellow LCD monitor outside the CPL. The image on the left should have a cooler color temperature. Similarly, the yellow tone of the right image should be slightly heated (the monitor is a little more blue than normal outside of CPL view).

Circular polarizer, 0 ° rotation, reverse mountCircular polarizer, 90 ° rotation, reverse mount
Hoya circular polarizer, reverse mounting orientation, 0 ° (left) and 90 ° (right) polarization

I don't have the Cokin Varicolor, but I have the Singh-Ray Gold-N-Blue polarizer (same effect). Here is the Gold-N-Blue filter at 0 ° and 90 °, oriented for correct mounting:

Gold-N-Blue Singh-Ray polarizer, 0 ° rotation, mounted correctlyGold-N-Blue Singh-Ray polarizer, 90 ° rotation, mounted correctly
Singh-Ray Gold-N-Blue polarizer, normal orientation, at 0 ° (left) and 90 ° (right) polarization

Here is the Gold-N-Blue oriented for reverse mounting:

Gold-N-Blue Singh-Ray polarizer, 0 ° rotation, reverse mountGold-N-Blue Singh-Ray polarizer, 90 ° rotation, reverse mount
Singh-Ray Gold-N-Blue polarizer, reverse mounting orientation, at 0 ° (left) and 90 ° (right) polarization

I couldn't tell the difference between the Singh-Ray Gold-N-Blue filter mounted on front and back. But the degree of effect between Gold-N-Blue and a reverse mounted CPL is significant.

  • Also keep in mind that in real life, the effect of Gold-N-Blue (and Varicolor, I suppose) is not so pronounced to turn the world into Denver Broncos colors, or to make it look like a Michel Bay color film . Blue and gold / orange are extremely saturated here because the color-separated light of the LCD is already polarized (by definition being an LCD monitor).

Aerial photography: why does a polarizer lead to these strange images above the clouds?

A sheet of glass or plastic will typically have internal stresses. For glass and some transparent plastics, these lead to the birefringence patterns you see, when you make light (partially) polarized in them and then you see them through a polarizing filter. You can test this by using two polarizing filters, one in front and one behind, or holding the object in front of an LCD monitor and placing a filter in front. If your filter came in a clear case, it could be a good test object. You can find more information on the subject by looking for "polarizer" and "stress", "stress analysis" or "birefringence". In fact, the Wikipedia article on birefringence has a lot of information and some examples of images.

In its case, the sky provides a partially polarized light source, the airplane window produces the birefringence patterns and the polarizing filter makes them visible to the camera.