Night Vision – 3 Things You Need To Know When Choosing a Camera


Black night vision cameraIn this piece we look at the important issues surrounding home security cameras with night vision capability. One of the biggest complaints with many of the cheaper models is that they display faded colors in daytime recording. You will soon see why some models outperform others despite the similar product descriptions. We look deeper into the technologies responsible for these disparities. This article highlights what you need to know about night vision security camera systems. By the end of this page you will be able to choose your own night surveillance camera system with confidence.

NOTE: You can jump to any part of this post by clicking the links in the table of contents

Table of Contents

  1. IR Surveillance Camera Explained
  2. When there’s no Infrared Cut-off Filter
  3. The Benefits of an IR-corrected Lens
  4. Buyer Beware – Know what You’re Getting
  5. #1 The IR-Cut Filter – How it Works
  6. #2 Powerful Illumination (IR LEDs) Beam
  7. #3 Infrared Illuminators
  8. Final Thoughts

IR Surveillance Camera Explained

Night vision security cameras can see in the dark because they have IR (Infrared) surveillance technology. During daylight hours, quality cameras use something called an infrared cut-off filter (also IR cut filter or heat-absorbing filter). After sunrise, night vision cameras filter out mid-infrared wavelengths so that they don’t distort the daytime images and colors. This “filtering” allows the lens to pick up the same colors as the human eye and so record natural looking images.[1]

When there’s no Infrared Cut-off Filter

A common problem with cameras that don’t have infrared cut-off filters is that the IR light can wash out the colors of daylight. You need the infra-red light for night time vision of course, but it can cause problems with daytime image quality, and that’s not so good. This doesn’t happen when there’s an Infrared cut-off filter fitted, but not all models have this and that’s the problem. Such cameras can end up a waste of money if the image quality is too poor. A mechanical IR-cut filter switch, therefore, is the solution. We’ll look into the mechanics of these filters in a moment.

The Benefits of an IR-corrected Lens

You can now see why not every night vision home security camera is equal in image quality. IR-corrected lenses not only improve image clarity but they also prevent out-of-focus images. Lost focus is something that can happen when switching between daytime and night modes. Remember, any night-vision security camera system is only as good as its image (videos or stills). This is why you need to know what you’re buying before you buy it. Most of them offer great things on the packaging, but they don’t all tell the full story or deliver on their promises.[2]

Buyer Beware – Know what You’re Getting

When you go shopping for night vision cameras you will come across wording like “Infrared (IR) Illumination.” This “night vision” is not only good, it’s essential for night time security, but alone it’s not enough. In fact, it’s one of the sales ploys to get you to add the product to your shopping basket.

The three main features to look out for include the following:

  1. IR cut filter
  2. Powerful illumination
  3. Infrared illuminators (ideally these match the FOV (Field of View) of the camera’s lens.

The day and night time quality of the camera system all comes down to these three features. I will now break them down for you one at a time to illustrate their importance:

#1 The IR-Cut Filter – How it Works

Night vision cameras with infrared cut-off filters don’t suffer any loss of daytime image quality. The way these filters work is actually simple, but it’s smart technology all the same.

When the camera’s lens picks up daylight (white light), it physically moves the Infrared cut-off filter over the lens to block out the IR light that would otherwise affect image quality. Likewise, the camera will move the lens out of the way as soon as light levels drop to the point where it needs night vision to record. The result of this “filter switch” is better image quality round the clock. If you stand close to these cameras you can actually hear an audible click sound as the lens move in and out of position.

Without the IR-cut filters there is no way to prevent full-spectrum light. The result then would be daylight images that suffer from distortion, that is, display pink-greyish hues that lack depth and a possible loss of focus.

#2 Powerful Illumination (IR LEDs) Beam

There is illumination and there is powerful illumination. You want to look out for the latter, and the more powerful it is the better your night vision will be. Ideally, when looking for an outdoor home CCTV camera, look for cameras that produce something in the neighborhood of 100 ft. of IR illumination.[3]

#3 Infrared Illuminators

To understand the common problem with infrared illumination we need to first look at Field of View (FOV). You can think of FOV by imagining you’re looking through a pair of binoculars. Everything you see is the binocular’s FOV and what you can’t see is outside the field of view. Often the infrared illuminators in a night vision security camera don’t match its FOV. In other words, the IR-beam is not illuminating the total area captured by the lens. This means it’s not recording everything it should be, or not recording anywhere near as well as it should be for the entire FOV. It’s akin to standing outside at night shining a spot light into a dark area.

Night vision cameras that have an IR illuminator narrower than the FOV means you get a bright area in the middle of the image capture. This image, like the spotlight effect, is darker the further from the center you look. It’s an effect that makes identifying areas outside the center difficult if not impossible. The solution to this problem is to choose the right night vision camera system. You want one that has an integrated IR illuminator that is equal to the camera’s FOV. This is the only way to get a reliably clear video throughout the entire image area. It might cost a bit more, but it’s worth every cent.

Final Thoughts

Not all night vision cameras are equal but the packaging on all models makes an impressive read. If you’re going to invest in home camera security with night vision, you want night vision that works well. You may as well invest in the best as it’s probably going to last you for many years. Seriously, try not to skimp if you don’t have to. Look for a system that has infrared cut-off filters, around 100 ft. of IR illumination, and also IR illuminators that are equal to the camera’s FOV.

You know how the good ones work and what makes them superior, so you’re now in a position to make a well-informed decision going forward.

Resources

  1. https://en.wikipedia.org/wiki/Infrared_cut-off_filter
  2. https://www.scribd.com/document/137620516/i-r-Corrected-Lenses-White-Paper
  3. http://whatis.techtarget.com/definition/near-infrared-illumination


About Mark Bickmore

Hi, my name is Mark Bickmore. I'm an Engineer, who has a keen interest in home security and keeping my family, property and valuables safe from burglars. This website was set up to help me explore the research, facts and myths about burglars and burglary. Please feel free to contact me should you have any questions, comments or suggestions.

Leave a comment

Your email address will not be published. Required fields are marked *