For anyone on the water being able to see and navigate in the dark has always been a challenge. Radar and chart plotters help us find our way but they have their restrictions. Today, technology that once was reserved for military use is now available to any boater who wishes to see and navigate in the dark; however, despite the many options now available to the consumer, not all products are equal in their abilities. Differing technology and image quality dictate the need for boaters to educate themselves on the products available along with their capabilities and drawbacks.
When most people think of night vision they think of those green fuzzy images created by Image Intensifiers. Once the only option, these devices take available light and magnify it creating a visible image. This technology allows low or very low light to be magnified and create a distinguishable image that is a vast improvement over the naked eye. Several generations of this technology evolved and each improved in quality, contrast and brightness. Early models were capable of magnifying light up to 1,000 times, with the latest generation capable of magnifying available light up to 40,000 times. This version of night vision has proved to be very popular and can be one of the least expensive on the market. Despite helping in some night or low light conditions they do have their drawbacks. They are light intensifiers and as such need some kind of light to operate. If there is no light they will not produce an image. They are also prone to ‘blooming’. This is simply a bright light that when seen by the device is also magnified and can cause the whole image to get lost in a ‘bloom’ of light. They also do not do well defining objects floating in the water such as debris because they are dependent on reflected light. Despite their disadvantages they are a cost effective option and can certainly be better than nothing at all.
Newer technology known as thermal imaging address some of the problems of image intensifiers and are remarkably effective at illuminating the dark even in complete darkness. The science behind thermal imagers is complex but not hard to understand. These devices contain a sensor that creates an image just like a digital camera uses its sensor to create an image or picture when you press the shutter. The difference is the camera uses light that strikes the pixels on the sensor to create the image, while the thermal imager uses heat energy, not light, to create that image. These imagers and their sensors can see long-range infrared radiation, which is well beyond what the human eye can see (10-30 times longer wave length). This means that these imagers can detect very minute differences in temperature and the rate they are giving off that heat. As a result they can create an image drawing out those differences, giving a very clear view even if there is no light at all. The key to these clear images is that everything gives off radiated heat including ice and even a log floating in the water. The differences in temperature create contrast which in turn creates a clear image. Cooler objects display as darker on the image while hotter parts of the image will show lighter, with white being the hottest. Thermal imagers are so sensitive that you can actually place your hand on a wall and withdraw it and still see the imprint of the hand before the ambient temperature of the wall returns.
There are varying sensitivities to these imagers and the Vanadium Oxide (VOX) microbolometer sensors within them. Just like in digital cameras the larger the sensor the better the image. At the bottom of the scale is a 160×120 sensor. This is very common among many lower cost thermal imagers on the market today. These images tend to be grainier and have less contrast than other sensors such as those offered by FLIR, a leader in thermal imaging. They offer imagers in 320×240 pixels and also in 640×480 pixels with four and eight times the image quality. If you were to lay a 160×120 sensor on top of a 320×240 sensor it would only be a fourth of the size. A 640×480 is a whopping eight times greater. A larger sensor directly relates to better images with more contrast and further reach. A larger sensor also translates to better resolution when you zoom (only available on some models). Zooming is ‘digital zoom’ where you increase the size of the pixels to get a closer look. If there are more to increase, each pixel is less affected and gives a clearer image. There are many models to choose from and FLIR has a wide array of imagers including a thermal imager that attaches to your iPhone turning it into a hand-held real time thermal scope. There are also monocular hand-held units as well as permanently mounted models, such as their marine M-Series and Voyager Series, some including gyro stabilization. These thermal imagers not only work exceptionally well in low or no light conditions but also work well in very bright conditions where the sun on reflected water might blind an operator. Their drawbacks are few other than cost, or the image being degraded by temperature blocking rain or fog. They can turn darkness into a close assimilation of daylight and, regardless of the model you choose, you will be able to see in the dark. The question is how much is that sight worth to you and how clear do you want to see?
While prices may be considered high by some they are now lower than ever before with more options for the mariner. As the price drops – and word of their effectiveness spreads – the future looks bright for thermal imagers.
Glenn Hayes is a freelance photographer and writer specializing in marine and location photography. His work covers commercial, editorial and fine art work. He lives in Florida and can be reached at:www.HayesStudios.com