Testing Polarizing Filters on HD Cameras

By: Ethan Ace, Published on May 30, 2014

Sun glare is particularly challenging for surveillance cameras. Even top cameras struggle with such conditions.

One technique suggested is using polarizing filters. Simply put, these filters pass certain polarizations of light, while blocking others, reducing sun glare at specific angles. 

To test how polarizers worked in real world scenarios, we tested 720p cameras in three configurations:

  • Auto-iris lens with polarizing filter
  • Auto-iris lens, no filter
  • P-iris lens, no filter

We tested these three cameras outdoors on a bright, sunny day, to see how the polarizing filter impacts performance.

Key Findings

Here are our key findings from this test:

  • Properly aligned polarizing filters can reduce sun glare significantly compared to unfiltered P-Iris and DC auto iris lenses, with the ability to see subjects through glass otherwise obscured by glare and reflection.
  • Small changes in angle of incidence impact filter effectiveness due to the narrow polarizations passed by the filter.
  • Low light performance was marginally degraded with the filter on, with little practical impact.
  • P-iris lenses provide a marginal improvement in visibility over standard DC auto iris lenses, but glare and reflection is still a significant issue.

Recommendations 

Polarizing filters can definitely help to reduce or eliminate sun glare in outdoor scenes. However, camera placement and angle of incidence need to be carefully considered if they are to be used, as polarization will only remove glare from narrow angles, not the entire scene. Cameras should be placed with this in consideration, in locations where repeatable angles are most likely in order to maximum the effectiveness of the filter.

Filter Mounting Types

Get Notified of Video Surveillance Breaking News
Get Notified of Video Surveillance Breaking News

There are two common types of filter mounts available:

Slip ring: This type of mount attaches to the front of a standard lens via a ring secured with set screws. Slip ring mounts and filters are available in 
multiple sizes to accomodate different lenses. Since the filter is mounted to the front of the lens and is essentially a flat piece of glass, focus of the lens remains nearly unchanged. Pricing varies from about $20 to $50 USD for sizes suited to CS mount lenses, but may run over $100 for larger filters used in photography.

C-Mount: C-Mount filters add an adapter between the lens and camera with a rotating ring built in to align the filter. This allows for more integrated package with less chance of the filter being bumped or removed in installation. However, since these adapters add distance between the lens and imager, focus is affected. C-Mount adapters sell for about $100+ online [link no longer available], not including the filter, generally another $50-100, making for a more expensive package overall.

Filter Setup

We used a slip ring filter from Midwest Optical Systems in this test. In this video we show how the filter is installed, with a threaded ring mounted to the lens:

Polarizing Alignment

In this video we show how to properly align the filter for glare reduction, and show angle issues. In this example, we are able to reduce glare on either the windshield or side windows of the car, but not both. Because of this, shots with filtered cameras should be carefully considered for best effectiveness.

Vehicle Glare

Positioning the cameras to view the front-right of the vehicle, the windshield of the car brightly reflects the sun in the low left corner, with sky and clouds reflected across the rest of the glass. The camera with the polarized filter can see our subjects skin tone, black shirt, and facial structurewhile the other two cameras only see the glare of the sun and reflection of the sky off the windshield.

Next, we moved to a frontal shot of the car, with significant windshield glare. Using the polarizing filter, windshield glare is nearly eliminated and we can clearly see our subject in the car. The unfiltered cameras, both standard and P-Iris, are unable to see him, though the P-Iris lens is marginally better. 

Low Light Impact

We tested the polarizing filter at night to see what impact, if any, it had on low light performance. In a low light scene, about 1 lux, the image is noticeably darker with the filter attached, seen in this overview shot with our subject in the car:

However, practical differences are small, seen in the image below. While the chart is slightly darker, it is no less legible with the polarizing filter on, and details of our subject are similar.

Test Methodology

All cameras were tested using 1/30s max shutter at 10 FPS with quantization ~28 average. All other settings were left default.

Cameras used in this test and their current firmware version:

  • Polarized 720p: Bosch NBN-733V, firmware 5.90
  • Standard 720p: Bosch NBN-733V, firmware 5.90
  • P-Iris 720p: Samsung SNB-5004, firmware 1.13_131218

1 report cite this report:

Vehicle Entrance Camera Selection Guide on Jul 21, 2015
When it comes to vehicle surveillance, the conversation regularly turns to license plate capture. But other information, such as identifying...
Comments (17) : Members only. Login. or Join.

Related Reports

Integrated IR Camera Shootout 2020 - Avigilon, Axis, Bosch, Dahua, Hanwha, Hikvision, Panasonic, Uniview, Vivotek on Jan 30, 2020
The best and worst cameras tested in this IPVM shootout showed major differences in quality and performance. While many view IR as being a...
Camera Focusing Tutorial on Oct 14, 2019
Camera focus is fundamental to quality imaging. Mistakes can significantly reduce details, making cameras less effective. In this guide, we...
Hikvision Acusense Analytics Tested on Sep 23, 2019
Hikvision touts "The Magic Behind It All" in their new Acusense line are 'deep learning algorithms' inside these cameras and recorders. But how...
Lens Iris Tutorial on Aug 08, 2019
Cameras, like humans, have irises, controlling the light which hits the imager and impacting image details. However, cameras have multiple types of...
Axis ARTPEC-7 P1375-E Camera Tested on Jul 12, 2019
Axis claims the new P1375-E box camera with ARTPEC-7 chip delivers "clear, sharp images in any lighting condition." But how well does it do? We...
Axis Live Privacy Shield Analytics Tested on Jun 25, 2019
Privacy is becoming a bigger factor in video surveillance, driven both by increased public awareness and by GDPR. Now, Axis has released Live...
Speco Ultra Intensifier Tested on Apr 22, 2019
While ISC West 2019 named Speco's Ultra Intensifier the best new "Video Surveillance Cameras IP", IPVM testing shows the camera suffers from...
Hanwha Dual Imager Dome Camera Tested (PNM-7000VD) on Oct 18, 2018
Hanwha has introduced their first dual-imager model, the PNM-7000VD, a twin 1080p model featuring independently positionable sensors and a snap-in...
Genetec Clearance Face Detection / Redaction Test on May 14, 2018
Privacy regulations such as GDPR (EU Public Privacy), HIPAA (US Medical Privacy), and FERPA (US Student Privacy) are driving video surveillance...
Vivotek 12MP IR Multi-Imager Tested on Aug 09, 2016
A key weakness of multi-imager cameras is poor low light. While integrated IR has become dominant in cameras overall, it is still uncommon in...

Most Recent Industry Reports

Hikvision Illicitly Uses Back To The Future In Marketing on Jul 03, 2020
NBCUniversal told IPVM that Hikvision UK's ongoing coronavirus marketing campaign using NBCUniversal's assets was not allowed. Hikvision mass...
Verkada: "IPVM Should Never Be Your Source of News" on Jul 02, 2020
Verkada was unhappy with IPVM's recent coverage declaring that reading IPVM is 'not a good look' and that 'IPVM should never be your source of...
Vintra Presents FulcrumAI Face Recognition on Jul 02, 2020
Vintra presented its FulcrumAI face recognition and mask detection offering at the May 2020 IPVM Startups show. Inside this report: A...
Uniview Wrist Temperature Reader Tested on Jul 02, 2020
Uniview is promoting measuring wrist temperatures whereas most others are just offering forehead or inner canthus measurements. But how well does...
Dahua USA Admits Thermal Solutions "Qualify As Medical Devices" on Jul 02, 2020
Dahua USA has issued a press release admitting a controversial point in the industry but an obvious one to the US FDA, that the thermal temperature...
Access Control Online Show - July 2020 - With 40+ Manufacturers - Register Now on Jul 01, 2020
IPVM is excited to announce our July 2020 Access Control Show. With 40+ companies presenting across 4 days, this is a unique opportunity to hear...
Hanwha Face Mask Detection Tested on Jul 01, 2020
Face mask detection or, more specifically lack-of-face-mask detection, is an expanding offering in the midst of coronavirus. Hanwha in partnership...
UK Government Says Fever Cameras "Unsuitable" on Jul 01, 2020
The UK government's medical device regulator, MHRA, told IPVM that fever-seeking thermal cameras are "unsuitable for this purpose" and recommends...
Camera Course Summer 2020 on Jun 30, 2020
This is the only independent surveillance camera course, based on in-depth product and technology testing. Lots of manufacturer training...
Worst Over But Integrators Still Dealing With Coronavirus Problems (June Statistics) on Jun 30, 2020
While numbers of integrators very impacted by Coronavirus continue to drop, most are still moderately dealing with the pandemic's problems, June...