Crushing hotspots, an introduction to Cross Polarization - Beverage Photo
Having a keen understanding of how to control and shape light is extremely important in product photography, in fact, it’s critical. Every product photographer should know how to apply cross-polarized light. Cross-polarization photography is key to reducing or eliminating unwanted highlights.
Reflections and hotspots can break the viewer’s ability to fully connect with the image and is simply an ugly distraction. However, cross-polarization photography, if done correctly, adds a level of professionalism to your imagery and can save time and money in post-production.
Polarized light offers a more aesthetically pleasing image and provides a softer light with smooth gradients and a more professional look.
Do you have everything you need to be a product photographer? For a comprehensive list of equipment to get you started in product photography, check out fellow ProEDU community member Tomás Arthuzzi’s recent article, Lighting & Gear Needed To Start Product Photography at ProEDU.com
What is Cross-Polarization?
Cross-Polarization Photography is the method of taking two linear polarizers - a polarizing film at the light source and a polarizing filter at the lens - and rotating both polarizers opposite each other to further dim light or cause what is known as light extinction.
Glare and reflection can become problematic when working with glass, liquids, and reflective surfaces. These surfaces can capture the photographer’s light sources, set up, or the photographer themselves. This is easily controlled by rotating linear polarizers against one another, as cross-polarization offers more control over reflective surfaces.
In order to execute cross-polarization effectively, you will need several items in your arsenal, all of which can be found at Adorama.com.
At the Light Source:
- Rosco Labs #7300 17”x22” Linear Polarizer Sheet
- A Beauty Dish that provides the ability to freely rotate the dish at the speedring while attached to your light source
- A 30° Grid applied to the beauty dish and light source provides a softer directional light
At the Lens:
How Does A Linear Polarizer Work?
In an effort to explain the mechanics of polarizers and polarized light, I reached out to Joel Svendsen, Content Marketing Manager at Rosco Labs, to learn more about linear polarizers and how they are designed to work.
A linear polarizer is divided into a series of columns, as depicted here. Some columns allow light to pass through - while others reduce the amount of light from reaching the subject. Joel explains “The 7300 Polarizing Filter itself reduces the light by 1.5 stops, as do most polarizing camera filters, so you’ll need to push 3 stops in order to compensate if you’re using this technique.”
This, at times, is not enough to block all the light waves because light bounces in various directions allowing the light to still leave a decent amount of glare. As shown in the next image, adding a polarizing filter at the lens and rotating the filter creates a misalignment of the columns and serves to further reduce the amount of light and glare.
Note: Not all polarizers are created equal. “One downside to this technique is that – because the Rosco 7300 and the camera polarizing filter are not made using the same polarizing material – as you cross-polarize towards extinction - you’ll start to see a color shift.” So be very mindful of color-shift when getting your cross-polarization boogie on.
Above in the #BTS Balvenie image, you’ll notice hotspots on the neck and in the base of the bottle.
One thing to note. When there are multiple hot spots, glares and reflections, there will be occasions where a simple turn of the polarizer will address multiple issues at once. However, there will be more instances where you’ll need to turn your polarizer multiple times to effectively eliminate hotspots throughout the subject.
The best way to know where your polarizers are most effective during your shoot is by matching the polarizer's location to an imaginary dial of a clock.
Pro Tip: Like the numbers of a clock, use the tension pin to remember where in the rotation the polarizer was its most effective. To do this, use the tension pin on the beauty dish at the speed ring, and on the Lee Filters compendium hood & bracket mount.
The key is to address the polarizers one at a time until you have reached the desired amount of dimming or removal of light created by your light sources.
Once the top light is in place and the set and subject are in their desired positions, begin rotating the polarizer to get an idea of where the light is being polarized where it is not.
You may be able to see the changes as you rotate the polarized light on the subject or set, but I highly recommend addressing this through the viewfinder of your camera.
As you can see in the Budweiser images (SOC) below, just a simple 45-degree turn of the filter at the lens knocked down the glare by approximately 98 percent on the bottle’s neck and label.
Where there are gains there will be losses. So as you work your polarizers against one another, there are a few things you’ll want to keep in mind.
When performing cross-polarization photography, the amount of light from your light source will be significantly reduced. So, don’t be alarmed if you find yourself using faster camera settings than you normally would when using strobes. You may find areas that once had the perfect highlight begin to suffer after the rotation of the polarizers.
And remember, when using polarized light with liquids and plastics, (especially clear plastics like acrylic ice or staging blocks) be mindful that this process could create some undesired color shifts such as browning or spectrums.
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